A blockchain is a decentralized, distributed ledger that records transactions on multiple computers so that the record cannot be altered retroactively without the alteration of all subsequent blocks and the consensus of the network.

Blockchains are often used to secure and validate transactions within a digital currency, such as Bitcoin. They can also be used to track the ownership and transfer of other types of assets, such as real estate, artwork, or intellectual property.

In a blockchain, each block contains a list of transactions and a unique code called a “hash” that links it to the previous block in the chain. This creates a secure, chronological record of transactions that is resistant to tampering or revision. The decentralized nature of blockchains means that they are not controlled by any single entity, but are maintained by a network of users who contribute their computing power to validate and record new transactions.