Cryptocurrency is a digital or virtual currency that uses cryptography for security. It is decentralized and operates independently of a central bank or government. Transactions are recorded on a public digital ledger called a blockchain. The most popular and widely-used cryptocurrency is Bitcoin, but there are many other types of cryptocurrencies such as Ethereum, Litecoin, and Ripple. These digital currencies can be used for online transactions, purchases, and even as an investment. However, the value of cryptocurrencies can be highly volatile, and they are not yet widely accepted as a form of payment in most places. Additionally, there are concerns about their potential use for illegal activities, such as money laundering and fraud.