Unless i'm mistaken, what they appear to be doing is appending emoji's to the end of an urban slang inspired hack-word (y.at) and suggesting that this has some kind of value...
In practice, then, they are selling web addresses like this: e.g. y.at/emoji1emoji2.
The fact is 'though, "Yat", as a reference, is virtually meaningless (I believe it's supposed to mean "you at"...), and emoji's are, at best, somewhat confusing.
In addition, Google will probably (effectively) ban these addresses through their Chrome browser by declaring that, on addresses that use emoji's, there's a "fake site ahead". They did this recently with symbol-based names such as €.com, etc...
To me, Y.at's offering is, to put it kindly, worthless... Y.at are, I think, the latest example of a severely over-heated NFT market, and when the dust settles on all of this madness then domain hacks will definitely get more attention.