Bitcoin (BTC) is the original cryptocurrency, launched in 2009 by the pseudonymous Satoshi Nakamoto. It introduced the first working combination of a public, decentralised blockchain and a consensus mechanism (proof of work) that let strangers agree on a shared transaction history without a bank or government in the middle.
Bitcoin's monetary policy is deliberately simple and slow to change: a hard cap of 21 million coins, a fixed and predictable issuance schedule, and a network that prioritises security and stability over flexibility. That's a large part of why many people treat it primarily as a form of digital, scarce money rather than a general-purpose computing platform.