In general a morph is a color and or pattern mutation that is genetic and that someone has proved out and stuck a name and a dollar value on. There are genetic variations that are still considered just normal.

If you want to learn the morphs then there are a lot of books you can pick up from the bigger breeders that have a lot of pictures but are a few years old and somewhat outdated but a good start. Otherwise you can just visit some of the bigger name breeders sites and they usually have a nice array of balls you can look at and how they came bout -- I think NERDs site probably has the most extensive information on morphs.