A good starting point for such generic questions is Wikipedia. At the main page just enter 'nikon mount' or 'f mount' and the first link presented will get you straight to the topic: Nikon F Mount. The very same idea works for any other camera-specific term, be it aperture, lens, filter .. you might get a selection page when the same term has more than one meaning. Select the the one referring to photographic context.
Another good website about Nikon equipment is Ken Rockwell. The guys has collected a good amount of information about Nikon cameras, including lens and camera compatibility list. Very helpful for beginners. However, don't take all his opinions for face value. He uses irony at times and some of his statements gave other photographers a good laugh.
