A cryptocurrency exchange, or a digital currency exchange (DCE), is a business that allows customers to trade cryptocurrencies or digital currencies for other assets, such as conventional fiat money or other digital currencies.
Most exchanges are more focused on providing services to help you exchange a cryptocurrency such as Bitcoin, into other digital currencies like Ethereum, Litecoin, etc. There are currently three types of exchanges out there: centralized or CEX, decentralized or DEX, and hybrid.