What is a blockchain, and why is it growing in popularity?

Bitcoin was the start, but as a wise man once said, you ain't seen nothing yet.

A blockchain is a ledger of records arranged in data batches called blocks that use cryptographic validation to link themselves together. Put simply, each block references and identifies the previous block by a hashing function, forming an unbroken chain, hence the name.

Put like this, a blockchain just sounds like a kind of database with built-in validation—which it is. However, the clever bit is that the ledger is not stored in a master location or managed by any particular body. Instead, it is said to be distributed, existing on multiple computers at the same time in such a way that anybody with an interest can maintain a copy of it.