A cryptocurrency exchange is a digital platform where users can buy, sell, or trade cryptocurrencies. There are two main types: centralized exchanges (CEXs) like Binance and Coinbase, which are run by companies, and decentralized exchanges (DEXs) like Uniswap, which operate through smart contracts. Exchanges vary in terms of fees, supported assets, security, and features. They play a crucial role in the crypto ecosystem by providing liquidity and access to digital assets.