What are decentralized exchanges (DEX)?

Decentralized exchange (DEX, decentralized exchange) Is an exchange, which works on the basis of a distributed ledger, does not store funds and personal data of users on its servers and acts only as a platform for finding matches on requests for the purchase or sale of user assets. Trading on such platforms takes place directly between the participants (peer-to-peer) without any financial intermediaries. Moreover, most of the existing exchanges, calling themselves decentralized, are not really completely like that: they use their own servers to store data on trades and orders to buy or sell user assets, however, the private keys are kept by the users themselves.