I've worked with textures and applying them to 3d object (more particularily a Vert[4] face). My question is: what is shown on the back side of the face the texture is applied to? Is it just a copy of the texture or is it black? (I'm at work and not on the computer my project is on other wise I'd look at it)

In general, if backface culling is enabled, nothing is shown at all. Otherwise, the exact same thing appears on both sides.

You may, of course, be using some special engine or API that modifies this behavior.