What is Blockchain and smart contract?

• Blockchain is a specific type of database.
• It differs from a typical database in the way it stores information; blockchains store data in blocks that are then chained together. 
• As new data comes in it is entered into a fresh block. Once the block is filled with data it is chained onto the previous block, which makes the data chained together in chronological order.
• Different types of information can be stored on a blockchain but the most common use so far has been as a ledger for transactions. 
• In Bitcoin’s case, blockchain is used in a decentralized way so that no single person or group has control—rather, all users collectively retain control.
• Decentralized blockchains are immutable, which means that the data entered is irreversible. For Bitcoin, this means that transactions are permanently recorded and viewable to anyone.

Smart contract is a smart contract is a computer program or a transaction protocol which is intended to automatically execute, control or document legally relevant events and actions according to the terms of a contract or an agreement.