A blockchain is a shared digital ledger that records transactions in linked blocks across many computers at once. Because copies are held across the network, no single party holds the only record.

How it works

New transactions are grouped into blocks, checked by the network through a consensus mechanism, and then linked to the chain. Cryptography ties each block to the last, making the history transparent and very hard to alter.

Why it matters

This design lets people transact without a central middleman and underpins cryptocurrencies, smart contracts and many other applications.