The snake world genetics are dumbed down ALOT so people can understand, so to break it down and make it easier:
"Dominant" = A snake that has no super form when bred to the same dominant animal
"Co-Dom" = A snake with a super form when bred back to the same Co-Dom snake
"Recessive" = Is the same as a co-dom animal (punnett square wise) but instead of being visual when it is "het" ,or carries 1/2 the needed genes for the animal to show visual, it is normal in coloration but still carries the gene.
List of animals that are in each category:
http://www.ballpython.ca/genetics.html