A shared, append-only ledger of transactions replicated across many independent computers and linked together by hashing, so mutually distrusting parties can agree on one history with no central operator.

It is really just a database with one expensive extra property: no single party controls the state. That property is what Bitcoin first used to let strangers transact peer-to-peer without a bank.

Go deeper:

• Blockchain — Wikipedia — the lead figure diagrams hash-linked blocks forming the chain.

A record of transactions that is replicated and synchronised across many nodes rather than held by one central authority, so every participant keeps and can verify the same copy.

A blockchain is the best-known kind of distributed ledger — one whose entries are grouped into hash-linked blocks. "Distributed ledger" is the broader category; not every distributed ledger chains its records into blocks.