Bitcoin is a payment system introduced as open-source software in 2009 by developer Satoshi Nakamoto. The payments in the system are recorded in a public ledger using its own unit of account, which is also called Bitcoin. Payments work peer to peer without a central repository or single administrator, which has led the US Treasury to call Bitcoin a decentralized virtual currency. Although its status as a currency is disputed, media reports often refer to Bitcoin as a cryptocurrency or digital currency. Bitcoin is often called the first cryptocurrency, although prior systems existed. Bitcoin is more correctly described as the first decentralized digital currency. It is the largest of its kind in terms of total market value.
Bitcoins are created as a reward for payment processing work in which users offer their computing power to verify and record payments into the public ledger. Called mining, GPU mining has become the main way to generate bitcoins. Besides mining, Bitcoins can be obtained in exchange for fiat money, products, and services. Users can send and receive Bitcoins electronically for an optional transaction fee using wallet software on a personal computer, mobile device, or a web application.