It's an autocross layout. What it it is a load of cones, tyre stacks etc. You can put checkpoints down and all that. It is a little bit like a new track, but they're normmally in the autocross environment or the Blackwood Car Park. It's limited, but fun :-)
You pop the lyt file (if you've been given one), in the X:\LFS\data\layout folder. Next time you load the track, you'll find that the layout has been loaded for you.
If you want to unload it, whilst you're on the track press Shift + U (press space if theres no GUI), and click "Clear all" in the bottom right.
If you want to load a lyt, make sure you're on the right track, press Shift + U and click "Load Layout".
I wouldn't go that far, it has been a while since I last loaded LFS and I just hit Hot Lap by reflex. Still, it wasn't specified in this thread nor the included Documentation (which I read). I hope it is helpful to someone else. Or maybe I'm just illepall