DEXs enable trustless and permissionless swaps.
A cryptocurrency exchange is an online platform where users can buy and sell different crypto assets.
The more decentralized an exchange is, the more it will allow any user anywhere to connect and trade directly, without the need for any intermediary. We call these Decentralized Exchanges or “DEXs” for short, two examples being THORChain and Sushiswap. DEXs, as stated, operate trustlessly and are permissionless, as opposed to a centralized exchange or CEX (e.g. Coinbase, Binance).
One of the drawbacks of CEXs is their power to restrict certain individuals or activities. US citizens for example cannot use Binance per US regulations. However, anyone in the world can use an open DEX freely by connecting with the proper wallet while retaining full custody of their coins, without needing to “create an account” or disclose their identity. This offers users from anywhere in the world a wide range of financial services that may otherwise be unavailable to them.
There are some tokens which can only be purchased on a DEX like Uniswap or Sushiswap. In that case, a peer-to-peer trade is the only option, so one must find the right DEX for their interests. Every blockchain network, as it matures, will see multiple DEX services, interfaces, and ways to access these trading platforms. Cross-chain DEXs such as THORChain and Osmosis even allow assets from different networks to be swapped natively.
Some crypto wallets provide swapping directly in the wallet; If you make a swap within XDEFI Wallet for example, you are using a particular DEX in the background (e.g. THORChain) without having to go to that dApp on the web.