Answer : Blockchain is a decentralized , distributed and public digital laser system where every piece of information is in block form. Each block usually contains a hash pointer , a timestamp, and transaction information as a link to the previous block . In this way blockchain is created by connecting one block after another. The first block is called the Genesis block. Since it is a distributed laser , the blockchain is usually operated with a pair-to-pair network. Each pair is called a node. And each node in the network has a copy of the blockchain. Once the data is recorded, the information in any block cannot be changed without the consent of the next block and without the consent of the network.