Glossary
Distributed Ledger
A database whose contents are replicated and synchronized across many independent nodes, with no single authoritative copy.
A distributed ledger is a database that lives on many machines at once, with every node holding the full history and applying the same rules. "Blockchain" is the most common shape of distributed ledger — a hash-linked chain of blocks — but other shapes (DAGs, for example) qualify too.
The point is that no node is privileged; if one is compromised or goes offline, the network keeps running and the surviving copies remain authoritative.