Bitcoin is a decentralized, peer-to-peer digital currency. Unlike money issued by a central bank, no single company, country or person controls it. Instead, Bitcoin runs on an open network of computers around the world that all follow the same set of rules, and it lets people send value to one another directly, without a bank or payment processor sitting in the middle.

Bitcoin was introduced in October 2008 by a pseudonymous creator (or group of creators) known as Satoshi Nakamoto, who published a short technical paper titled "Bitcoin: A Peer-to-Peer Electronic Cash System." The network itself went live in January 2009, when the first block of transactions - the "genesis block" - was created. Nakamoto's real identity has never been confirmed and they stopped participating in the project publicly a couple of years after launch.

Every Bitcoin transaction is recorded on a public, shared ledger called the blockchain - a chain of "blocks," each containing a batch of transactions. New blocks are added through a process called mining, part of a system known as proof-of-work: computers on the network ("miners") compete to solve a computationally difficult puzzle, and whoever solves it first gets to add the next block and is rewarded with newly created bitcoin. This process makes it extremely expensive to rewrite transaction history, which is what keeps the ledger trustworthy without needing a central authority to vouch for it.

One of Bitcoin's defining features is that only 21 million bitcoin will ever exist. This limit is enforced by the software every participant on the network runs, not by a promise from any company. New bitcoin enters circulation as the block reward paid to miners, and that reward is cut in half on a fixed schedule (an event known as "the halving") until, eventually, no new bitcoin will be created at all.

People value Bitcoin for different reasons: its fixed, predictable supply in contrast to currencies that can be printed without limit; its resistance to censorship, since no government or company can freeze or reverse a properly broadcast transaction; and its decentralization, since the network keeps running even if individual computers, companies or countries stop participating. This has led some to describe it as "digital gold" - a potential store of value - though that view is a market narrative, not a guarantee, and Bitcoin's price has historically been highly volatile.