Blockchain.
In plain English
A blockchain is a record of transactions kept in identical copies across a network of computers rather than by one central authority. New transactions are grouped into blocks and linked in a chain, and the network agrees on each block, which makes rewriting old entries very difficult. It is the technology under cryptocurrencies like Bitcoin, but the idea is broader: any shared record where participants do not fully trust a middleman. Whether it is genuinely useful for a given job is a separate question from the marketing around it.
01Why it matters
Blockchain is the technology behind crypto and a lot of financial marketing, so understanding what it actually does helps you cut through the noise.
02The math, step by step
When someone sends Bitcoin, the transaction is broadcast to thousands of computers that each update their copy of the blockchain, rather than one bank updating a private ledger.
03What this is NOT
A blockchain is NOT the same as Bitcoin. Bitcoin is one cryptocurrency built on a blockchain; the blockchain is the underlying record-keeping technology, which many other projects also use.