How is a decentralized exchange (DEX) different from a centralized exchange (CEX)?

Unlike CEXes, no central authority or third party is involved in the operation of a DEX. As a result, a user retains full control of their funds stored or traded on DEXes, which offer a higher degree of security than CEXes. While CEXes are believed to be faster and offer generally better user experience than DEXes, the latter have recently shown significant improvements in those areas.