Bitcoin is a decentralized digital currency that was invented in 2008 by an unknown person or group using the name Satoshi Nakamoto. It is a peer-to-peer system that enables transactions to be made without the need for a central authority or intermediary, such as a bank. Bitcoin transactions are recorded on a public digital ledger called the blockchain, which is maintained by a network of computers around the world. Bitcoins can be bought and sold on cryptocurrency exchanges and can also be used to purchase goods and services from merchants who accept them as payment. The total supply of bitcoins is limited to 21 million, with around 18.7 million already in circulation as of 2021.