distributed ledger

A distributed ledger is a record of entries — who owns what, who paid whom — that is stored across many computers at once, with no single official copy. Each computer holds its own full version, and the network constantly works to keep all those copies in step. The goal is to remove the single point of control (and single point of failure) that a traditional central database has.

In an ordinary system, a bank or a government keeps the one true ledger, and you simply have to trust that they have not edited it, lost it, or been hacked. A distributed ledger flips that around: because hundreds or thousands of independent copies exist and must agree, there is no master record to quietly alter and no single server whose failure takes the whole system down. To change the shared truth, you would have to convince a majority of the network at the same time.

A blockchain is the most famous kind of distributed ledger, but not the only one — the defining idea is many synchronized copies plus a rule for agreeing on updates, however the data happens to be structured. This design is what lets a payment network or registry keep running honestly even when nobody is in charge and some participants are offline or dishonest.