A blockchain is a public ledger of all transactions that have ever been executed. A block is the “current” part of a blockchain that records some or all of the recent transactions, and once completed, goes into the blockchain as a permanent database. Each time a block gets completed, a new block is generated. Blocks are linked to each other (like a chain) in proper linear, chronological order with every block containing a hash of the previous block. To use conventional banking as an analogy, the blockchain is like a full history of banking transactions. The transactions are entered chronologically in a blockchain just the way bank transactions are.