The components are from other photos, literally millions of them ( i think they just scoured google images, or picasa, or something), and they have all been sampled into a huge neural network that recombines the elements (nose, eyes, mouth, etc) into new photos using some clever image stiching and colour correction. If you refresh it enough you can sometimes see similar features here and there, but thats easily fixed by using a larger database of source material. Even so its scarily realistic.
Like i said there is also one that can take a non-nude, and make it nude (called deep nude, but there are others) but its nowhere near as good. You have to get the exact right combination of elements before its believable but its only a matter of time.
But those combined with the full motion deep fake technology (
External Link/Members Only ) you are going to find it near impossible to believe anything you see online, or on TV, in the near future.