dtailmycar- Welcome to Autopia!
Abrasive products are just that, they mechanically remove paint like sandpaper removing wood. It's exactly the same principle as sanding a scratch out of a piece of wood and the only realy way to eliminate marring (swirls/scratches/etc.). OTC choices include Mother's Power Polish and Meg's Scratch-X.
Chemical cleaners will give a clean surface and remove oxidation, but won't do much of anything for marring. Example: Meg's Deep Crystal Step #1.
Glazes (as the term is normally used) are like "makeup for cars". They hide imperfections but don't really solve the underlying problem so the imperfections appear to "come back". Examples: Meg's Deep Crystal Step #2 and Meg's #7.
Sealants are basically just synthetic waxes. The often won't stick to glazes whereas wax will. Some like Meg's NXT will stick to most glazes.
Going to an autobody/paint supply store (check the yellow pages) will radically expand the definition of "OTC". You can order anything you'd like and they usually have lots of good stuff on the shelves. These "pro" products are the way I've gone since I was a kid.
Edited because I just found out that Meguiar's Color-X contains both chemical cleaners and diminishing abrasives; I'd thought it was abrasive-free. But don't let that put you off it; abrasives aren't categorically a bad thing and these are *VERY* mild.
