A cryptocurrency is a type of digital or virtual currency that uses cryptography to secure and verify transactions as well as to control the creation of new units. Cryptocurrencies are decentralized, meaning they are not issued or controlled by any central authority such as a government or financial institution. Instead, they rely on a distributed ledger technology called blockchain, which is a public record of all transactions made with the cryptocurrency. The most well-known cryptocurrency is Bitcoin, but there are now thousands of different cryptocurrencies in circulation. Some popular examples include Ethereum, Litecoin, and Ripple. Cryptocurrencies can be bought and sold on exchanges, used to purchase goods and services, or held as a speculative investment.