Cryptocurrency is a form of digital currency designed to work as a medium of exchange through a computer network that is not reliant on any central authority. This decentralization makes cryptocurrencies theoretically immune to government interference or manipulation. Most cryptocurrencies are built on blockchain technology, which is a distributed ledger enforced by a network of computers (nodes). Popular cryptocurrencies include Bitcoin, Ethereum, and Ripple which use various mechanisms for transaction verification, maintaining security while allowing for transparent transactions.