Pastillas is made from condenesed milk, powder milk and sugar.
Yema is the Spanish word for yolk and probably refers to either the confections appearance as a spherical yellowish sweet candy or to the fact that it contains quite a bit of egg yolks. Made with just a few ingredients - condensed milk, egg yolks, dayap (lime) zest for flavoring, yemas are intensely rich and especially so when they are coated in caramelized sugar.
Polvoron is powdered milk candy, made of flour, sugar butter and powdered milk. The flour is toasted, all the ingredients are mixed and shaped into round or oval-shaped molds.