Bitcoin (BTC), the world's first decentralized cryptocurrency, was invented in 2008 by an anonymous entity known as Satoshi Nakamoto, who published its foundational white paper before its open-source implementation began in 2009. It operates on a peer-to-peer network, where transactions are recorded on a public, distributed ledger called a blockchain, validated through a computationally intensive "mining" process that has drawn environmental criticism. Key historical moments include the first transaction in January 2009 and the famous "Bitcoin Pizza Day" on May 22, 2010, when ₿10,000 bought two pizzas. From 2021 to 2025, El Salvador uniquely adopted Bitcoin as legal tender, a significant step for a digital currency. Despite its innovative nature, Bitcoin's pseudonymous use by criminals has attracted regulatory attention, leading to bans in several countries.