What is a Blockchain
A blockchain is an ever-growing ledger, a series of premanently recorded, cryptographically linked data structures or "blocks". Each block consists of the transaction data (a so-called Merkle tree), a timestamp, and the cryptographic hash of the previous block. Once recorded, the data inside of a blockchain cannot be modified without altering every single block within the blockchain. It has been described as a distributed ledger that records transactions between two parties in a permanent and efficient way.