projector fogs?

What specifically is meant by the term projector? Or, how do they differ from ordinary fogs? I saw some cheapo oval projector fog lights on sale that I am thinking of getting to mount in my new yet-to-be-built rear bumper to use as trail lights/rock lights. My concern is that they might need a certain 'shine distance' (tech term!) to work well, and I want to have them angled down instead of pointing straight out.
Any thoughts?

 

[Bill Kemp]

A projector light has a very sharp cut off of the light that would normaly go up. The light is focused down on the road. The beam pattern looks like a half a circle.
You probably should have them pointing out rather than down or the light wouldnt go out very far..

 

[RangerX]

Thanks, Bill. Sounds like they will work.
I won't point them straight down, just angled a little, due to my bumper height and my need to see what's right behind me offroad.