A ledger is simply a record of transactions, the same idea used in traditional accounting for centuries. What makes a crypto ledger different is that it is distributed: instead of one bank or company keeping the master copy, the record is shared across many computers that each hold an identical version.
This distributed design changes how trust works. In traditional finance, you rely on an institution to keep the ledger honest. On a blockchain, many independent participants each maintain the ledger and agree on updates, so no single party can quietly alter the record. Everyone can check that the shared history is consistent.
The blockchain itself is a type of distributed ledger, one that groups transactions into linked blocks. Not every distributed ledger uses that exact structure, but for cryptocurrencies the terms are closely related. The core benefit is a record that is transparent, shared, and very hard to tamper with.