DEX is the acronym for Decentralized Exchange.
A Decentralized exchange is a platform for individuals to trade assets between each other that is governed by multiple entities rather than a central single authority.
Decentralized Exchanges are profit driven organizations that custody its users assets on their books and thus have the ability to confiscate, censor, and freeze its users assets.
Decentralized exchanges are borne of the core crypto philosophy relating to owning private keys. Decentralized exchanges do offer incredible benefit of self sovereignty; meaning that users of the platform custody their own assets and do not run the risk of having their funds frozen or stolen by regulators.
However, due to their distributed natures, decentralized exchanges tend to have less volume, operate slower, and provide less liquidity as opposed to their centralized counterparts.