The technology that underpins most cryptocurrencies is blockchain. Blockchain is a decentralized ledger technology that securely records and verifies transactions across a network of computers. Each block contains a list of transactions, a timestamp, and a reference to the previous block, creating a chronological chain. This structure ensures transparency and immutability of data, as altering any block would require consensus from the entire network. The trustless nature of blockchain allows for secure peer-to-peer transactions without the need for intermediaries like banks.