Bitcoin (BTC) is the first and largest decentralised cryptocurrency, introduced in 2009 by the pseudonymous Satoshi Nakamoto. It belongs to the Layer 1 category as a base-layer settlement network and digital store of value, and it was created to enable peer-to-peer electronic payments without a bank or other trusted intermediary controlling the ledger.

The network is secured by a proof-of-work consensus in which miners compete to solve SHA-256 hashing puzzles, adding blocks of transactions roughly every ten minutes. This makes the transaction history extremely costly to alter and removes any single point of control. New supply is issued as a block reward that is cut in half about every four years in an event known as the halving, gradually slowing issuance toward the fixed maximum of 21 million coins.

Bitcoin is widely used as a store of value, a long-term reserve asset and a settlement layer, and it is increasingly held by institutions and accessible through regulated investment products. Its scarcity and predictable monetary policy are central to its appeal, while second-layer systems such as the Lightning Network aim to support faster, cheaper everyday payments. BTC remains the most recognised and most liquid cryptocurrency and is commonly treated as the market's benchmark asset.