Cryptocurrency is a form of digital or virtual currency secured by cryptography, making it nearly impossible to counterfeit or double-spend. It operates on decentralized networks based on blockchain technology, a distributed ledger enforced by a network of computers. Unlike traditional currencies, cryptocurrencies are not issued by central authorities, allowing for peer-to-peer transactions without intermediaries like banks. Popular cryptocurrencies include Bitcoin, Ethereum, and Litecoin. They are used for various purposes, from payments to investment and powering decentralized applications. While offering benefits like transparency and security, cryptocurrencies also face challenges such as regulatory uncertainty, price volatility, and environmental concerns from mining activities.