wet sanding vs dry sanding

Excuse my ignorance but why do both? Its obvious how they differ but what bennefits are there from doing both, I've always done it because thats all I've read but never really knew the reasoning behind sanding dry and then wet when you're in the primer/paint/clear stages of your project. Could somebody give me a quick synopsis? Just curiosity thats all.go custom or go home!!

isnt wet sanding just done to keep the sandpaper from clogging up and not screwing up the paint?  i would figgure the dry sanding would be left for sanding off origional paint and doing filler and all that, but when u get to the primer and paint stage u dont want to run the rist of scratches from clogged sandpaper.  I could be wrong though.

Dry sanding is the start of the project getting the imperfections out of whatever you're sanding. Wet sanding is towards the end to make things smooth as possible to get ready for the painting. ~The Rookie~

Rookie of the year that is...

Don't let the smoke out of your equiptment..it doesn't go back in.

I was always under the impression that wet sanding makes a smoother finish with the same grit paper, especially if the paper is made for wet sanding. Whether it is because of the clogging or the water making it sand less, I'm not exactly sure.

yeah, it's the same reason you use soap with a clay bar. the water kind of lubricates the paper, so it keeps sanding scratches down and finishes your project off nice and smooth before paint