Het stands for Heterozygous which basically means they carry the genes but its only visible in the Homozygous (Visible Morph) parents. Piebald, Albino, Axanthic, etc are all ressive morphs meaning that when the visible morph is bred to a normal all the offspring will be 100% Hets. Breeding a 100% het to a normal will result in the offspring being 50% hets but you cant tell which ones are hets because they all look normal. Co-Dom and Dominate are different from ressive morphs, breeding a co-dom or dom to a normal will result in visible morphs, but theres still that chance you dont get the morph. Pastel, Lesser, Mojave, Cinny etc are all examples of co-doms, co-dom meaning that breed 2 or the morphs and you could get the super or dominate form of the morph, ie Super Pastels, Leucistics, Super Cinny etc. Spiders, Pinstripes etc are dominate menaing that there is no Super form (yet). Hope this helps a little. Take a look at Nerds genetics page, its a real good read.