Bitcoin is a peer-to-peer cryptocurrency based on a Proof-of-Work consensus mechanism and a decentralized ledger called a blockchain. Satoshi Nakamoto developed Bitcoin in late 2008 and the network launched on January 3, 2009.
Bitcoin has a limited supply of 21 million bitcoin. Bitcoin also has no central controller. Instead of a single database which provides data to users, all users maintain identical copies of the database, called a blockchain. This blockchain records all transactions made on the Bitcoin network, allowing users to verify their balances and transaction history. Bitcoin’s blockchain is append-only, meaning new blocks can be added but old blocks cannot be removed or altered.
Since Bitcoin is both a protocol and a currency, the way it is capitalized depends on the context. Bitcoin with a capital B is used to refer to the network and the asset class, while bitcoin with a lowercase b is used to refer to the coin, which is transferred in Bitcoin transactions and has a market price.