blockchain

A blockchain is a shared record book that many computers keep identical copies of at the same time. Instead of one company owning the master copy, everyone on the network holds the same list of entries, and they all follow the same rules to agree on what gets added next. It solves a very old problem: how can strangers who do not trust each other agree on a single set of facts without a referee in the middle?

The name comes from how the data is packed. New entries (such as payments) are bundled into a group called a block, and each block carries a tiny fingerprint of the block before it. Chaining the fingerprints together means the blocks form a strict order, like beads on a string. If anyone tries to quietly change an old entry, its fingerprint changes, the next block no longer matches, and the tampering is obvious to everyone. This is what makes the history practically impossible to rewrite.

Because every participant keeps a full copy and the rules are public, no single party can secretly edit the past, block a valid entry, or print extra money for themselves. That is why a blockchain can power things like digital cash, ownership records, and self-running programs without needing a bank or a central administrator to be trusted.