Do you know how in WoW/Runescape you can walk up to another player and launch a trading window with them? Yeah, that, but for Cardano. If you're not familiar with those video games here is another take on it: have you ever wanted to swap an NFT for another NFT? Perhaps you wanted to do something even more complicated like trading 2 NFTsa and a bunch of Husky tokens against someone's adaHandle? Well, that is where Atomic Swap shines, enabling p2p swapping without the need for any intermediaries.
Atomic Swap only ever submits one transaction to the blockchain. It will move the assets between your two wallets at the exact same time. You can verify this by looking up your transaction on cardanoscan after you have made a successful swap. So there is no way for anyone to get screwed since your funds will only be transferred if they also transfer their funds at the same time.
All this is accomplished without the need for smart contracts. This is very good since it isn't needed! It means that the swap is faster (only one transaction instead of at least two), more secure (it vastly reduces the number of potential bugs), and cheaper (because there is only one transaction).