Bitcoin (₿) is a cryptocurrency invented in 2008 by an unknown person or group of people using the name Satoshi Nakamoto. The currency began use in 2009 when its implementation was released as open-source software.
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. Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services. Research produced by the University of Cambridge estimated that in 2017, there were 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.
Bitcoin has been criticized for its use in illegal transactions, the large amount of electricity used by miners, price volatility, and thefts from exchanges. Some economists, including several Nobel laureates, have characterized it as a speculative bubble at various times. Bitcoin has also been used as an investment, although several regulatory agencies have issued investor alerts about bitcoin.