Also known as a double sided material:
http://vimeo.com/50922887It's missing from a lot of models - clothing to be more specific. Such as:
- gauntlets (visible)
- armors/headgear (sometimes visible)
- garments (extremely visible)
Without double sided material/textures you can basically see right threw the clothing. Like when you look at the garments from a certain perspective/angle and turn around you'll see they are transparent on the inside. Same thing happens with certain types of gauntlets when you take a closer look.