What Are Cryptocurrencies? Blockchain & Bitcoin Explained

Learn what cryptocurrencies are, how blockchain technology secures transactions, and why Bitcoin started a 2.72 trillion USD digital currency market.

Introduction

Cryptocurrencies are digital currencies that use cryptography to secure transactions, control new units, and verify asset transfers. They operate on blockchain networks, which are distributed ledgers stored across many computers instead of one central server. Bitcoin, launched in 2009, was the first cryptocurrency and remains the largest asset by market influence.

The cryptocurrency ecosystem includes Bitcoin, alternative cryptocurrencies called altcoins, and stablecoins that link their value to fiat currencies such as the US dollar. These assets rely on consensus mechanisms such as proof of work and proof of stake, which coordinate transaction validation and coin creation without central banks. Users interact with cryptocurrencies through crypto wallets that manage private keys and through exchanges that process buying, selling, and trading.

On 1 February 2026, total cryptocurrency market capitalisation stood near 2.72 trillion US dollars, with Bitcoin holding about 56.8 percent market dominance. CoinPaprika tracked 57,598 currencies, more than 25,000 markets, and about 350 active exchanges at that time. These figures describe the scale and variety of the cryptocurrency market covered in this guide.

How does cryptocurrency work?

Cryptocurrency operates through a peer-to-peer network, a system where computers communicate directly without central servers. When Alice sends Bitcoin to Bob, her wallet creates a transaction message containing the amount, Bob's public address, and a cryptographic signature that proves ownership of the funds. Public addresses function like bank account numbers and receive funds, while private keys function like passwords and authorise spending from those addresses.

The transaction broadcasts to thousands of nodes, which are network computers that maintain and validate the blockchain. Each node verifies the transaction using cryptographic algorithms that confirm Alice holds enough Bitcoin and has not spent the same funds elsewhere. This process prevents double spending, where someone tries to use the same digital currency twice.

Validated transactions move into a temporary pool until miners or validators group them into a block, which contains many transactions. The network reaches consensus, meaning agreement on the next valid block, through mechanisms such as proof of work or proof of stake. The chosen block joins the blockchain, and each additional block strengthens the security of previous records.

Once the network confirms the block, the transaction becomes part of a permanent distributed ledger that all nodes store. Bob's wallet updates after several confirmations, which is often six blocks for Bitcoin, a process that takes roughly sixty minutes depending on network conditions.

What is blockchain technology?

Blockchain is a distributed ledger, a digital record of transactions stored across many computers rather than in a single database. Each transaction becomes part of a chronological chain of blocks that all network participants can verify. The ledger is public on most major networks, so anyone can inspect all recorded transactions.

Each block contains transaction data, a timestamp, and a cryptographic hash, which is a unique digital fingerprint produced by a mathematical function. The hash links each block to the previous block and forms a chain where altering an old transaction would require editing every subsequent block across the network. This structure makes recorded data effectively immutable after confirmation.

Blockchain technology functions like a shared spreadsheet that many computers update at the same time. When a transaction enters the system, nodes record it in a new block that joins the existing chain after consensus. This design removes the need for a single administrator and reduces reliance on traditional intermediaries such as banks.

Bitcoin: the first cryptocurrency

Bitcoin, launched in January 2009 by the pseudonymous creator Satoshi Nakamoto, was the first successful decentralised cryptocurrency. It solved the double-spending problem, where someone attempts to use the same digital currency twice, without using a central clearing house. Bitcoin combines cryptography, a distributed ledger, and a proof of work consensus mechanism to secure transactions.

Bitcoin uses proof of work, where miners run specialised hardware to solve mathematical puzzles and validate blocks of transactions. Miners compete to find a hash that meets the network's difficulty target, and the first successful miner broadcasts the block to the network. Other nodes verify the solution and then add the new block to the blockchain.

Bitcoin reward and supply table

Bitcoin remains the largest cryptocurrency by market capitalisation and adoption. It processes hundreds of thousands of transactions per day, with confirmation times that range from about 10 to 60 minutes depending on network congestion and transaction fees. Bitcoin's fixed maximum supply of 21 million coins supports its "digital gold" narrative among some investors who compare it with scarce assets.

Types of cryptocurrencies

Cryptocurrencies fall into several main categories based on their design and purpose. Bitcoin acts mainly as a store of value and medium for peer-to-peer payments. Altcoins, which are alternative cryptocurrencies launched after Bitcoin, cover many functions such as smart contracts and decentralised applications. Stablecoins aim for price stability by linking their value to fiat currencies, often at a one-to-one ratio.

Major cryptocurrency categories

Bitcoin focuses on security and decentralisation through proof of work, which requires high energy consumption but resists many attack types. Ethereum supports programmable money through smart contracts that run on its virtual machine, and it now uses proof of stake to validate transactions with lower energy use. Stablecoins such as Tether and USD Coin maintain a stable price target and see frequent use in trading pairs and cross-border transfers.

What is decentralisation?

Decentralisation distributes control and decision-making across many network participants instead of concentrating power in one authority. Traditional fiat currency systems rely on central banks and governments to issue money, manage supply, and supervise payment networks. Cryptocurrency networks distribute transaction validation across peer-to-peer networks of nodes that apply the same protocol rules.

In a decentralised peer-to-peer network, any participant can run a node that stores a copy of the blockchain and validates transactions. The Bitcoin network operates through thousands of nodes worldwide, which reduces dependence on any single entity. When a transaction enters the network, nodes verify that it follows protocol rules and then include it in blocks through consensus.

Why decentralisation matters

Decentralisation provides censorship resistance because no single entity can block, freeze, or reverse valid transactions once the network confirms them. Banks and payment processors can refuse payments or freeze accounts, but public cryptocurrency networks process transactions that follow protocol rules regardless of sender identity.

Decentralisation increases transparency because the blockchain ledger is public and auditable, so anyone can review transaction histories. It also increases user control because private key holders decide when to transfer their assets, without account managers or bank officers. These advantages come with trade-offs, including irreversible transactions and the absence of central customer support for lost keys or mistaken payments.

How are cryptocurrencies created?

New cryptocurrency units emerge through consensus mechanisms, which are rules that networks use to validate transactions and add blocks to the blockchain. Earlier networks such as Bitcoin rely on proof of work, while newer or updated networks such as Ethereum rely on proof of stake. These mechanisms replace central banks in controlling money creation.

What is cryptocurrency mining?

Cryptocurrency mining is the process that proof of work networks use to create new coins and validate transactions. Miners group pending transactions into candidate blocks and then search for a hash that meets the network difficulty target by repeatedly hashing block data. The first miner that finds a valid hash broadcasts the block to the network.

Other nodes verify the block's validity and then add it to the blockchain. The successful miner receives the block reward plus transaction fees as compensation. Bitcoin miners currently earn 3.125 BTC per block after the April 2024 halving, down from 6.25 BTC. This reward halves about every four years, which slows new supply growth.

Proof of work vs proof of stake

Proof of work and proof of stake are two common consensus mechanisms that secure blockchains and create new currency units. Proof of work uses computational energy to secure the network, while proof of stake uses staked cryptocurrency.

Consensus mechanism comparison

Proof of work ties security to the cost of computing power and electricity, which makes attacks expensive but raises environmental concerns. Proof of stake ties security to the value of staked currency and uses mechanisms such as "slashing", where networks confiscate stake from dishonest validators.

What are crypto wallets?

A crypto wallet stores private keys, which are cryptographic codes that prove ownership of blockchain addresses and authorise transactions. Cryptocurrencies exist on the blockchain, not inside the wallet, and the wallet manages the keys that control those funds. Each wallet manages a key pair consisting of a public key, which generates addresses for receiving funds, and a private key, which signs outgoing transactions.

Private keys are long random numbers, often expressed as 256-bit values, which attackers cannot feasibly guess with current computing power. When a user sends cryptocurrency, the wallet uses the private key to create a digital signature that proves ownership without revealing the key itself. If someone loses a private key or the recovery phrase backing it, they lose permanent access to the associated funds because blockchains do not support password resets.

Types of crypto wallets

Cryptocurrency wallets group into categories based on internet connectivity and who controls the private keys. Hot wallets connect to the internet and support frequent transactions, while cold wallets store keys offline to reduce attack surfaces. Custodial wallets place keys under the control of a service provider such as an exchange, while non-custodial wallets give key control to the user. Hardware wallets are physical devices that store keys in secure chips.

Wallet category comparison

Hardware wallets such as Ledger and Trezor use secure element chips, which are tamper-resistant components also used in passports and payment cards. Ledger devices use CC EAL5+ certified secure elements, while newer Trezor models use EAL6+ certified chips to strengthen physical security.

What are cryptocurrencies used for?

Cryptocurrencies support several financial and technological uses beyond speculation. Digital payments form a core use, where people send value directly between digital addresses without banks processing transfers. Bitcoin often functions as a store of value and inflation hedge for investors who want alternatives to local currencies. Cross-border remittances use cryptocurrencies and stablecoins to reduce fees and settlement times compared with traditional wire transfers.

Smart contracts extend cryptocurrency use by encoding self-executing agreements on blockchains. When predefined conditions occur, the smart contract executes transactions according to the code, without lawyers or manual approval. Ethereum supports many smart contract-based applications, including decentralised exchanges and lending platforms. Decentralised finance, or DeFi, uses smart contracts to provide lending, borrowing, and interest-earning services without banks. Users deposit cryptocurrency into protocols such as Aave or Compound and receive interest or borrowings secured by collateral.

Non-fungible tokens, or NFTs, represent unique digital items such as art, music, in-game assets, or diplomas on blockchains. Each NFT has a distinct identifier in the ledger that proves ownership and authenticity. NFT trading volumes expanded sharply between 2021 and 2022 and then declined during 2023 and 2024. NFTs also support identity credentials, supply chain tracking, and event ticket verification.

Cryptocurrencies also support programmable money, where smart contracts release funds based on dates or conditions, and governance tokens, where holders vote on protocol parameters. Some gaming projects integrate cryptocurrencies and NFTs to manage in-game currencies and user-owned items that trade across markets. Remittances remain an important application: a 2023 study reported that about 10 percent of the 5 billion US dollars in Venezuelan remittances used cryptocurrency rails.

What are the risks and challenges?

Cryptocurrencies involve several significant risks. Price volatility stands out, as Bitcoin's price fell from about 69,000 US dollars in November 2021 to roughly 16,500 US dollars one year later, a drop greater than 75 percent. Researchers report annualised Bitcoin volatility around 80 percent in some periods, much higher than major stock indices. This volatility affects portfolio values and complicates the use of cryptocurrencies as stable means of payment.

Security risks remain frequent. Reports for 2024 record more than 400 hacks and security incidents at cryptocurrency services, with estimated losses around 2.01 billion US dollars. Decentralised finance protocols and cross-chain bridges accounted for a large share of stolen funds. Many incidents stem from exchange breaches, private key theft, phishing, and smart contract bugs. Users who lose private keys or recovery phrases lose permanent access to funds due to the irreversible design of blockchain transactions.

Blockchain transactions are effectively irreversible once the network confirms them. Bitcoin transactions are usually treated as final after six confirmations, which generally requires about one hour. This design reduces chargeback fraud but removes consumer tools such as refunds through payment processors. Mistyped addresses or transfers to scammers cannot be reversed through the protocol.

Risk categories table

Scams present another challenge. Rug pull schemes, where developers abandon projects and withdraw liquidity, caused about 106 million US dollars in losses across 58 incidents in 2024. Reports highlight fake tokens, phishing websites, and Ponzi-style investment programmes among common fraud types.

Regulation varies widely across jurisdictions. Some countries recognise cryptocurrencies as legal to trade and hold under anti-money-laundering rules, while others impose bans or strict restrictions. The European Union adopted the Markets in Crypto-Assets (MiCA) framework in 2024 to harmonise rules for issuers and service providers. United States regulators, including the Securities and Exchange Commission and Commodity Futures Trading Commission, apply existing securities and derivatives laws to many crypto activities as of 2024–2025.

How to get started with cryptocurrency

Getting started with cryptocurrency involves five main steps. A new user researches assets, selects a reputable exchange, creates and verifies an account, deposits funds, and makes a first purchase. Identity checks follow know-your-customer standards and require documents such as passports or national IDs. Many beginners start with small purchases of Bitcoin or Ethereum while learning how transactions and wallets function.

Choosing a cryptocurrency exchange

Cryptocurrency exchanges are platforms where users trade digital currencies against fiat currencies or other cryptocurrencies. Key evaluation factors include security controls, regulatory oversight, fees, asset listings, and geographic access. Reputable exchanges use two-factor authentication, hold most customer funds in cold storage, and may offer insurance for custodial balances. Licensed exchanges in regions such as the European Union, United States, and United Kingdom operate under specific regulatory frameworks and must follow anti-money-laundering rules.

Trading fees affect total costs. Many centralised exchanges charge maker fees between 0.1 and 0.5 percent and taker fees between 0.2 and 1.0 percent per trade. Asset variety also matters: large exchanges list major currencies like Bitcoin, Ethereum, and leading stablecoins, and may list additional altcoins, while smaller platforms focus on a limited selection. Some services restrict access by country because of licensing or sanctions, so residents of certain regions cannot open accounts on specific platforms.

Centralised exchanges such as Coinbase, Binance, and Kraken hold user funds in custodial wallets and manage private keys on behalf of customers. These platforms often provide easier interfaces, customer support, and direct fiat deposits and withdrawals. Decentralised exchanges run as smart contracts on blockchains and route trades between user wallets without central custody. Users connect their non-custodial wallets and trade directly from their own addresses, but must manage keys and interact with blockchain interfaces themselves.

FAQ

References / Sources

• CoinPaprika. "Cryptocurrency Market Overview" and "Pricing & Market Intelligence API." CoinPaprika.com, accessed February 2026.
• Nakamoto, Satoshi. "Bitcoin: A Peer-to-Peer Electronic Cash System." Bitcoin.org, 2008.
• Ethereum Foundation. "Ethereum Proof-of-Stake and The Merge." Ethereum.org, 2022–2024.
• OECD and academic literature on decentralised finance and NFTs. Various journals and surveys on DeFi and NFTs, 2021–2024.
• Global crypto policy and regulation reports. TRM Labs and Investopedia regulatory overviews, 2023–2025.
• Security and risk analyses of cryptocurrency markets. Studies and industry reports on hacks, volatility, and risk management, 2018–2025.