Blockchain is a distributed ledger technology that allows for the transparent, secure, and immutable recording of transactions. It's made up of a network of computers, called nodes, that store and validate data in blocks. Each block contains a cryptographic hash of the previous block, linking them together in a chain. Transactions are verified and approved by the network, and once a transaction is added to the chain, it can't be changed or deleted. So, in short, blockchain is a secure and transparent way to record information.