Bitcoin is a cryptocurrency and worldwide payment system. It is the first decentralized digital currency, as the system works without a central bank or single administrator. The network is peer-to-peer and transactions take place between users directly, without an intermediary. These transactions are verified by network nodes through the use of cryptography and recorded in a public distributed ledger called a blockchain.
Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services. As of February 2015, over 100,000 merchants and vendors accepted bitcoin as payment.
Research produced by the University of Cambridge estimates that in 2017, there are 2.9 to 5.8 million unique users using a crypto currency wallet, most of them using bitcoin. The word bitcoin first occurred and was defined in the white paper that was published on 31 October 2008.
It is a compound of the words bit and coin. The white paper frequently uses the shorter coin. There is no uniform convention for bitcoin capitalization.