lacquers are usually shellac, acrylic, nitrate(dope), butyrate(dope), with various acetates or ketones plus xylene and toluene solvents.
Vinyl and hydrocarbon resin, along with naptha, xylene and ethylbenzene are more like varnishes.
Varnishes and enamels use various kinds of alkyd resins and oils that will cure from oxygen in the air dissolved in mostly mineral spirits solvents.
Mostly lacquer is a name for a hard, sandable, solvent resistant clear finish. Polycrylic finishes usually are very hard and brittle, but sandable. They tend to raise the grain on raw balsa so a couple of coats of nitrate dope are needed to keep the wood smooth.
The zinc stearate bridges small gaps to keep the finish from soaking in too much and makes it more sandable.