Cryptocurrency is a digital or virtual form of currency that uses cryptography for security and operates independently of a central authority, such as a government or financial institution. Unlike traditional currencies like the dollar or euro, cryptocurrencies exist solely in digital form and rely on blockchain technology to record transactions and manage the issuance of new units.

Key features of cryptocurrencies include decentralization, meaning they are typically not controlled by any single entity; anonymity, as transactions can often be conducted pseudonymously; and security, thanks to cryptographic techniques that protect the integrity of transactions and the creation of new units.

Bitcoin, created in 2009 by an anonymous individual or group using the pseudonym Satoshi Nakamoto, was the first cryptocurrency and remains the most well-known and widely used. Since then, thousands of other cryptocurrencies, often referred to as altcoins, have been created, each with its own unique features, purposes, and underlying technologies. Examples of popular cryptocurrencies other than Bitcoin include Ethereum, Ripple, Litecoin, and Cardano.