AA - Anti-Aliasing. In really basic terms, it blends object edges together so that you dont have hard pixellated (bumpy) edges to objects, but smooth ones that blend in with the background. It just takes a lot more precossing power to generate these extra "transitional" pixles with varying degrees of transparency. It's kind of like the difference between a CUT and a FADE in a video. The fade is a lot smoother, easier on the eyes, and much better looking. This explains it.
http://en.wikipedia.org/wiki/Antialiasing
AF - Anisotropic filtering. Put a piece of paper down on your desk. Then get down and look at it almost edge on. The paper appears just as wide, but much shorter from front to back because of your perspective. In games, the textures on objects at extreme angles tend to look stretched - because the computer is applying a square image to a long, thin polygon. Mip mapping (another effect) stretches the image beforehand so that it is applying a long, thin image to this polygon, and makes it look better. AF basically aids in this process by not only stretching the image to the correct proportions, but adjusting the amount of detail (more for the closer edge.) Again, this explains it in more depth.
http://en.wikipedia.org/wiki/Anisotropic_filtering
I hope that helps, and I hope I know what I'm talking about!
EDIT: Lol, in the time it took me to type all that, he edited his reply, and you two both posted. Dammit.