This is the best tutorial for gaining a basic understanding of what UV is, I have found,
en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/UV_Map_Basics#2.49b
It gives a brief look at unwrapping a 3D object in order to do game textures and realtime photoshop, gimp, ect. painting. This along with
otothecleaner.free.fr/tutorials/tutorials.html
Will enable any noob gamer to produce and use low memory, high quality textures.