A blockchain is a digital ledger that records data in a secure, tamper-proof way. It is distributed across a network of computers and is used to track transactions and store data. Each computer or node in the network stores a record of all the transactions that have taken place, creating an ever-growing list, known as the blockchain. Whenever a new transaction takes place, it is added to the chain, making it virtually impossible to modify or delete any of the data without approval from the entire network. This makes the blockchain an ideal technology for verifying information, maintaining data security and protecting against cyberattacks.