This sounds like a dumb question, but you know, if I don't ask it, I will stay dumb regarding this matter; so here it goes.

What is the difference between AF and AF-S?

Are AF-S silent/faster than AF? I do see that they are more expensive; so better construction? Better glass? Sharper images?

Again, sorry for my ignorance, but hey, I tried reading and finding some information about it and couldn't in the Nikon forum and in the leses review it is pretty vague since Nikon there are only about 5 lenses reviewed.