Get yourself a copy, it is a very valuable resource. This discussion is brief, not a course for enameling and staining glass. To assure individuals seeking instruction, this is a source for a start.
Vitreous paint is a mixture of ground glass and pigment, sold in a powdered form.
A binder and mixing agent hold the paints on the glass. Firing the stains and enamels in the kiln, provide a permanent adhesion. Stains do not color the glass with bright transparent shades. The major colors are black, several browns, flesh reds, and gray-greens. The enamels are transparent colors.