Bitcoin is a decentralized digital currency and peer-to-peer payment network introduced in 2009 through a whitepaper published under the pseudonym Satoshi Nakamoto. It operates on a proof-of-work consensus mechanism using the SHA-256 hashing algorithm, with miners validating transactions and securing the network. BTC has a fixed maximum supply of 21 million coins, with new coins issued through block rewards that halve approximately every four years.