For Russians, Poles, etc, kasha can mean other grains, but in US/UK usage is means a buckwheat grain (often crushed to various "granulations"), often toasted, used for pilaf type preparations, or breakfast cereal. One source of confusion is that buckwheat is not even related to wheat -- it's in a family with rhubarb. And very good for you!

No. Bulgur is wheat, kasha is buckwheat. http://www.foodsubs.com/GrainBuckwheat.html
http://www.foodsubs.com/GrainWheat.html