All the car's UV files in one folder for simplicity! Just unpack it and leave the UV folder on your desktop and whenever you want to make a skin take it out of this folder instead of having to go through all those folders and whatnot.
He's not the only one who's done it. I know some skins using unofficial UVs were made for the second gen Pessima. I really want some official UVs though, because I have some planned skins for the T-Series that I'm itching to make.
A UV map is what allows you to skin vehicles in beamng, you put it in whatever photo editing program and it shows you were to draw or edit in order to make a skin
I recommend you check the wiki to show you how to make a skin. Or find a video on YouTube. There is a lot more to skinning than just drawing on a car.
Adviced to use the ones in the game itself instead (each skinnable vehicle has the UV_Layout available in its folder), as we might update some of them from time to time..