Blockchain is a decentralized and distributed digital ledger technology that records transactions across multiple computers in a network. It allows for secure, transparent, and tamper-proof storage and transfer of data or value without any central authority or intermediary. The information on the blockchain is stored in blocks which are linked together using cryptography, forming an unalterable chain of evidence. Blockchains are most commonly associated with cryptocurrencies like Bitcoin but have a wide range of potential applications across various industries such as supply chain management, voting systems, and identity verification.