A blockchain is a list of blocks in cryptocurrenciies. Cryptocurrencies are virtual currencies rather than paper/metallic money. Each block, of the blockchain, is actually a record. The blocks associated with each other under the safest technologies. Each record has a cryptographic hash of the previous history including a timestamp and transaction detailed data. The timestamp denotes the time of creation and alteration in the document. The distributed ledger records the exchange of currencies between buyers and sellers efficiently. It is managed through a peer-to-peer network. New blocks are validated by the individuals who observe the practice. A record can’t be altered without modifying all blocks that linked to it, and this needs the involvement of the network majority. It was discovered by 'Santoshi Nakamoto' in 2008, for bitcoin transactions and public records.