What is blockchain?

A blockchain is the record-keeping system behind Bitcoin and other cryptocurrencies. Think of it as a shared notebook that thousands of computers keep an identical copy of.

Transactions are grouped into 'blocks'. Each new block is linked to the one before it, forming a chain — hence 'blockchain'. Once something is written into the chain, changing it would require rewriting every copy on thousands of computers at once, which is practically impossible.

This is what makes crypto work without a bank: instead of trusting one company to keep honest records, everyone can check the shared record themselves.

Blockchains are used for more than money — tracking goods, proving ownership of digital items, and running programs called 'smart contracts' — but their first and biggest use is cryptocurrency.