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.
According to research produced by Cambridge University in 2017, there are 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, its high electricity consumption, price volatility, and thefts from exchanges. Some economists, including several Nobel laureates, have characterized it as a speculative bubble.
Bitcoin has also been used as an investment, although several regulatory agencies have issued investor alerts about bitcoin.
The first bitcoin transaction took place on January 3, 2009, when Nakamoto sent ten bitcoins to an early adopter. The first transaction recorded in the first block of the blockchain was a single transaction paying the reward of 50 new bitcoins to its creator.