Firstly found a better pic for it:-

Originally Posted by
painter
2x, 4x, 8x, and 16x determines how detailed the anisotropic filtering is.
For me, anti-aliasing has a very high processing cost whereas anisotropic filtering is pretty minimal.
Anisotropic filtering will typically give you a better overall experience between the two AF and AA. Without it on, textures will look muddy & dull.
Anisotropic filtering = Sharper textures at a distance.
Antialiasing = Jagged edges of rendered 3d objects are smoothed.
In most games, One will have anisotropic filtering maxed (16x) and AA off/2x or 4x depending on the game. Beyond 4xAA you see diminishing returns and the performance hit (which often comes with mouse lag on less powerful cards(main culprit)) isn't worth the difference between say, 4xAA and higher antialiasing.