Blockchain is a kind of shared database that differs from traditional databases in the way data is stored. Here blockchains store data in blocks that are then cryptographically linked together. As new information is received, it is entered into a new block. Once the block has been filled with data, it is chained into the previous block, forming a chronological chain of data. A blockchain can hold a variety of data, but the most widely used application has been as a transaction ledger. In short, blockchain is employed in a decentralised manner. There is no single person or group which has control over the system. All users have collective control. It offers transparency.