Bitcoin, introduced in 2008 by Satoshi Nakamoto (an unidentified programmer or group of programmers), is an open-source, peer-to-peer cryptocurrency and an electronic payment system. The transactions between users are direct, without intermediary. These transactions are verified by a global network of "nodes" and recorded in a public distributed ledger called the blockchain, which uses bitcoin as its unit of account. Since the system works without a central repository or single administrator, bitcoin is called the first decentralized digital currency. Bitcoin is the largest of its kind in terms of total market value.
Bitcoins are created as a reward in a competition in which users offer their computing power to verify and record bitcoin transactions into the blockchain. This activity is referred to as mining and successful miners are rewarded with transaction fees and newly created bitcoins. Besides being obtained by mining, bitcoins can be exchanged for other currencies, products, and services. When sending bitcoins, users can pay an optional transaction fee to the miners. This may expedite the transaction being confirmed.