In the basic sense, rendering is the final stage in the 3D graphics pipeline once you have modelled, shaded and lit your scene. It is the process you use to produce your final images.

Texturing is the process of applying images (textures) to your 3D models to make them look the way you want them to look, for example, you would texture a cylinder with the image of some tree bark if you want it to look like a tree.

You can find out a lot more about these processes by looking in the Maya help files, and there's tons of stuff on the web.

LisaG