Block

A block is a batch of transactions packed together and added to the blockchain in one go. Think of a page in an accounting book: once it's full and approved, it gets sealed and a fresh page starts.

Each block carries a timestamp and a unique digital fingerprint (a hash) of the block before it. Change one transaction in an old block and its fingerprint changes, breaking the link to every block after it. That chain of fingerprints is what makes history so hard to rewrite.

Blocks are created by miners or validators, who earn a block reward for the work. How often a new one arrives is the block time.