Three kinds of venues: exchanges, DeFi, savings apps

Custodial exchanges (CEX): you move coins to the exchange, which holds the keys for you. Easy, but your funds are only as safe as the exchange: if it fails or is hacked, you stand in line with its creditors.

DeFi: you keep your own wallet and deposit into a smart contract. Nobody holds your funds, but a bug or an exploit can lose them, and there is no customer service.

Savings apps in wallets or in Telegram are usually a layer over one of the two: their risk is the layer below plus the app’s own.

A "DEX" is where you swap coins, not where you deposit for interest.