Buckwheat is not wheat at all. Nor is it a grain or cereal. It comes from the seeds of a flowering plant, Fagopyrum esculentum which is related to Sorrel, Knotweed and rhubarb. It is gluten free. The triangular seeds, known as groats, can be ground into a sort of flour which is used for making noodles, crepes and many other gluten free products.

Despite it's name, buckwheat is not related to wheat:

http://en.wikipedia.org/wiki/Buckwheat

A derivative of normal wheat I think