Blockchain is a decentralized and distributed digital ledger that records transactions in a way that is permanent, transparent, and secure. It is essentially a database that is continuously updated and verified by network participants, rather than a single central authority. The database consists of blocks of data, each of which contains a series of transactions and a unique identifier, or hash. Once a block of transactions is verified and added to the blockchain, it cannot be altered, ensuring the integrity and immutability of the data. This technology is primarily associated with cryptocurrencies, but has potential applications in a wide range of industries including finance, healthcare, and logistics.