Bitcoin is a decentralized digital currency, without a central bank or single administrator, that can be sent from user to user on the peer-to-peer bitcoin network without the need for intermediaries. Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain.
Bitcoin is unique in that there are a finite number of them: 21 million.
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 University of Cambridge estimates that in 2017, there were 2.9 to 5.
8 million unique users using a cryptocurrency wallet, most of them using bitcoin..