My car is getting painted right now and im just curious what is stage 2 paint vs stage 1 or 3??

Single stage is a base/clear mixture sprayed all at once

2 stage paint is basecoat/clear coat sprayed seperately so that your clear coat is just clear, and entirely free of any base, this makes the compound and polish process easier and generally gives a much better finish

3 stage paint is specialty paint, usually associated with expensive pearl paints