About five thousand years ago, people invented writing to keep track of their dealings with each other. This started on clay tablets, and eventually moved onto paper bound into books. In accounting speak, such books have a technical name – ledgers.
With the advent of money came cash books, or cash ledgers. Just think of them as private diaries for money.
Businesses today still maintain their own proprietary cash books. It may be on a computer rather than paper, but the purpose of a modern multinational’s cash ledger hasn’t changed since the paper cash books of old: to record and keep track of payments, receipts, balances and dates.
What’s this got to do with Bitcoin? Everything. Because even though it’s public rather than private, that’s essentially what Bitcoin is: a cash ledger, or cash book.
Bitcoin is a book.