A distributed, immutable digital ledger that records transactions across a network of computers.
A blockchain is a distributed database that maintains a continuously growing list of records (blocks) linked together cryptographically. Each block contains a hash of the previous block, creating an immutable chain where altering any past record would require changing every subsequent block — making tampering practically impossible. Blockchains operate across a peer-to-peer network of computers (nodes), with no single point of control or failure. Different blockchains use different consensus mechanisms (Proof of Work, Proof of Stake, etc.) to agree on which transactions are valid. The technology was first implemented by Bitcoin in 2009 and has since expanded to support smart contracts, DeFi, NFTs, supply chain tracking, digital identity, and more. Public blockchains are transparent and permissionless; private blockchains restrict access for enterprise use.
A blockchain is a distributed ledger technology where transactions are grouped into blocks, cryptographically linked in chronological order, and replicated across thousands of independent nodes — making the record practically immutable. The innovation isn't any single technology but their combination: cryptographic hashing ensures data integrity, consensus mechanisms coordinate agreement among untrusted parties, and economic incentives (mining rewards, staking yields) make honest behavior profitable. Beyond cryptocurrencies, blockchain technology enables programmable agreements (smart contracts), verifiable digital ownership (NFTs), and decentralized organizations (DAOs). The technology faces fundamental scaling trade-offs described by the 'blockchain trilemma': it's difficult to simultaneously optimize for decentralization, security, and scalability. Different blockchains make different trade-offs: Bitcoin maximizes security and decentralization; Solana maximizes speed; Ethereum pursues a rollup-centric scaling roadmap to balance all three.
The Ethereum blockchain processes roughly 1 million transactions per day across DeFi, NFTs, L2 rollups, and token transfers — all publicly verifiable by anyone running a node.
No — blockchain is the underlying technology (a type of distributed ledger), while cryptocurrency is one application built on it. Blockchains can support many applications beyond currency: smart contracts, supply chain tracking, digital identity, voting systems, and more. Not all cryptocurrencies even use traditional blockchains (IOTA uses a DAG structure).