What is a ledger, and what does it do?

A ledger is a record of who owns what and how it changed hands. Every bank, business and government department keeps one. A cryptocurrency is, at its core, a ledger that is shared among many computers and not kept by any single institution.

What does a ledger do?

A ledger has four jobs:

• Record. It writes down every transfer: who sent, who received and how much.
• Order. It fixes the sequence of transfers, so everyone agrees which came first.
• Prove ownership. The current balances follow from the full history, so the ledger is the evidence of what belongs to whom.
• Prevent double spending. Before a new payment is accepted, the ledger shows whether the sender still has that money.

A good ledger also leaves an audit trail. Anyone allowed to read it can check how a balance came to be.

How is a bank's ledger different from a blockchain's?

When you send money through a bank, the bank edits its own private ledger. You trust the bank to keep it accurate, and only the bank and its regulators can see inside.

A blockchain turns that around. The ledger is public, and thousands of computers called nodes each hold a full copy. New entries are grouped into blocks and added only when the network agrees they are valid, through a consensus mechanism. Once a block is buried under later ones, changing it would mean redoing the work of the whole network, which is why the record is treated as permanent.

This design is called a distributed ledger. It removes the need to trust one record keeper. The cost is speed: getting thousands of computers to agree is slower than letting one bank update a database.

Does the ledger hold my coins?

Yes, in the sense that matters. Your coins are not stored in an app or on a device. They are entries on the ledger, tied to an address. A crypto wallet holds the private key that lets you sign new entries moving those coins.

Is this the same as a Ledger wallet?

No. Ledger, with a capital L, is a company that makes hardware wallets, which are small devices that store private keys offline. The name is borrowed from the concept. A crypto ledger in the general sense is the blockchain's record itself.