Ive watched a lot of paint jobs on different shows and i was wondering what the differce is between sealer and primer? iV seen them put what they call sealer on the car, do the body filler work then primer it.

The sealer will keep the bare metal from rusting while you do the actual bodywork on the car. If you simply spray a coat of primer on it, it will begin to rust when moisture gets to it.

Actually a primer is for bare metal to provide adhesion and corrosion protection. Ex's would be etch primer and epoxy primer.

A primer SURFACER is the product you block sand for perfection. Its meant for filling small minor surface imperfections. It prodvides no corrosion protection.

A primer SEALER is used for providing a uniform color and aid in adhesion prior to final painting.
It also provides no corrosion protection and many sealers are just converted primer surfacers, thinned down for better spraying.

The topcoat those shows are using first is an epoxy primer.