Understanding Bitcoin

Bitcoin was introduced in 2008 as a way to send value directly between two parties without relying on a bank or payment processor to verify the transaction. The core technical challenge it solved is called 'double-spending': in a purely digital system, what stops someone from copying their money and spending it twice?

Bitcoin's answer is a shared, public ledger -- the blockchain -- maintained not by one company, but by a distributed network of independent computers (nodes) that all agree on the same transaction history using a consensus process called proof-of-work.