Bitcoin is a digital asset and a payment system invented by Satoshi Nakamoto who published it in 2008 and released it as open-source software in 2009. The system is peer-to-peer; users can transact directly without an intermediary. Transactions are verified by network nodes and recorded in a public distributed ledger called the blockchain.
The ledger uses bitcoin as its unit of account. The system works without a central repository or single administrator. It is the largest of its kind in terms of total market value.