A blockchain is a distributed ledger technology that records the movements of digital assets and maintains immutable records across multiple computers. It is a secure and transparent way for parties to transact with one another without the need for a third-party intermediary. Each time a transaction occurs, it is securely stored on a block, which is then added to the blockchain. This chain of blocks is continuously updated and maintained in agreement between all participants, eliminating the need for a central authority and preventing double-spending. The system also ensures that transactions are valid and secure by using cryptography to ensure the integrity of the data. By keeping records of all transactions and interactions, the blockchain provides a secure and transparent system for parties to conduct business with each other.