Blockchain is a digital ledger of transactions that is distributed over many computers. It is used to store and track secure, transparent and permanent records of data which can be used for various purposes, such as cryptocurrencies, smart contracts, and medical records. With blockchain, each piece of data is encrypted and linked to other pieces of data in a chain of blocks, providing an immutable record of the entire chain of events. Blockchain technology provides users with a faster, more secure and efficient way to conduct transactions.