Paint sealant is the term generally used to describe a 100% synthetic product that serves the same purpose as a wax - to protect the finish and preserve the high gloss achieved through proper prep (claybar, paint cleaning, polishing). Meguiar's NXT Tech Wax is a sealant, so is Zaino, etc.

Yes, you can use a sealant after claying. In fact, you can apply a carnauba blend over a sealant to alter or enhance (depending on your point of view) the appearance.