Decentralized exchanges, in any case, called DEXs, are circulated in business places where computerized money shippers make trades clearly without giving over the organization of their resources to a center individual or guardian.
These exchanges work using self-executing arrangements written in code called smart agreements. They are intended to automatically execute actions reducing the need for intermediates.

Since we know every scientific or technological advancement we reach, it somehow has some limitations. Let's look at the limitations of dex. We can only swap crypto for crypto in the agreement. The cryptos that were being interchanged or traded must be in the same blockchain technology. For example, if we use uniswap exchange we can only exchange Ethereum with Ethereum tokens. Sushiswap has extended to many blockchains but still, we cannot swap with another blockchain other than the blockchain token we have or we traded. In order to do inter Blockchain Token switching, we have to do Blockchain Bridges.

Advantages of dex :

1. DEX allows P2P trading of currencies. Where P2P stands for Peer to Peer.  it refers to a marketplace that links buyers and sellers.
2. Users keep control of the wallet's private key.
3. Users are not required to submit their KYC, i.e. decentralized exchanges without kyc or any personal information like SSC/social security number, fingerprinting, name, address, profile pictures cherishing their privacy. 
4. In DEX we have no centralized authority. Instead of relying on coinbase or binance, we trust Code. Code is called opensource here.
5. DEXs are faster than CEXes. 
6. Very less transaction fee than CEX.

Downsides of decentralized exchanges:

1. No support, if you have an issue you have no support/care system to whom you can call or mail. But you do have community forums, but they are not authorized by the bitcoin swapping exchanges.
2. In decentralized exchanges, you must have a Hot Storage Device. That means, your wallet must be connected to the internet.
3. Just like a sword with both sharp edges, the code is an open code, it's transparent to everyone, and it is also open to hackers for vulnerabilities.