Bitcoin

Bitcoin is a decentralised digital currency and the network that runs it. It was described in a white paper published on 31 October 2008 under the name Satoshi Nakamoto, and the network went live on 3 January 2009 with the "genesis block".

Instead of a bank keeping the ledger, thousands of independent computers (nodes) each hold a copy of a shared record of transactions called the blockchain. New blocks are added roughly every ten minutes by miners using proof of work, and the rules of the software cap total supply at just under 21 million coins.

Bitcoin can be split into 100 million smaller units called satoshis, so you can buy a tiny fraction of one coin. Ownership is controlled by private keys: whoever holds the key can move the coins, which is why self-custody and security matter. The price is set by trading on open markets and is highly volatile.