The bitcoin protocol is the foundational set of rules for a decentralized, peer-to-peer network that relies on a public ledger called the blockchain to record every transaction transparently and securely. Users broadcast signed transactions, which are verified by network nodes and grouped into blocks by miners who solve complex cryptographic puzzles—a proof-of-work process using SHA-256 hashing that demands significant energy but is cheap to verify. This proof-of-work system, the key innovation of the pseudonymous creator Satoshi Nakamoto, ensures a new block is added roughly every 10 minutes, with the longest valid chain considered the authoritative history. Due to the high costs of hardware and electricity, miners collaborate in mining pools, and after China's 2021 ban on mining, the United States now dominates this sector. Finally, any protocol changes require consensus among participants, and this technology has inspired countless other cryptocurrencies and applications like smart contracts and supply chain management.