1. What is blockchain?
One of the easiest-to-understand definitions of blockchain comes from a recent Harvard Business Review article written by Marco Iansiti and Karim R. Lakhani. They wrote, "blockchain is an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way."
A more detailed definition is available from Gartner's website, which says, "Blockchain is a type of distributed ledger in which value exchange transactions (in bitcoin or other token) are sequentially grouped into blocks. Each block is chained to the previous block and immutably recorded across a peer-to-peer network, using cryptographic trust and assurance mechanisms."
The key points are that data stored in a blockchain is distributed (as in Git repositories or file-sharing networks), highly secure, easily accessible and impossible to change. Those characteristics make blockchain ideal for recording financial transactions, but it could also be used in other ways.