Blockchain
A public, distributed ledger that records all Bitcoin transactions in chronological order.
Ledger
Definition
In traditional finance, a ledger is a book or database where a bank tracks who owns what. Bitcoin replaces this with a public ledger — the blockchain — that is maintained by thousands of independent nodes instead of a single institution.
Example
Unlike a bank's private ledger, Bitcoin's ledger is public — anyone can view every transaction ever made.