Bitcoin (BTC) is a decentralized digital currency, also known as cryptocurrency, that was invented in 2008 by an unknown person or group of people using the pseudonym Satoshi Nakamoto. It was launched as open-source software in 2009. Bitcoin operates without a central authority, such as a government or a bank, and transactions are recorded in a public, digital ledger called the blockchain.

Bitcoins are created through a process called mining, where powerful computers compete to solve complex mathematical problems in order to add a new block of transactions to the blockchain. As a reward for this work, the miner who successfully adds the block is rewarded with new bitcoins. The total number of bitcoins that can ever be mined is capped at 21 million.

Bitcoin transactions are made directly between users, without the need for intermediaries like banks. This allows for faster and often cheaper transactions, but it can also make the currency more susceptible to illicit uses, such as money laundering or buying illegal goods.

Since its introduction, Bitcoin's value has experienced significant fluctuations, making it a highly speculative and volatile investment. Nonetheless, it has inspired the creation of many other cryptocurrencies, collectively known as altcoins, and has sparked ongoing debates about the potential roles and impact of cryptocurrencies and blockchain technology in the global financial system.