In English, kasha usually refers to the pseudocereal buckwheat or its culinary preparations. In Eastern European cuisine, kasha can apply to any kind of cooked grain. It can be baked but most often is boiled, either in water or milk, and therefore the term coincides with the English definition of 'porridge', but the word can also refer to the grain before preparation, which corresponds to the definition of 'groats'. This understanding of kasha concerns mainly Belarus (каша), the Czech Republic, Lithuania, Poland, Romania and the Republic of Moldova, Russia (каша), Slovakia, Slovenia, Kazakhstan, and Ukraine (каша), where the term, besides buckwheat, can apply to wheat, barley, oats, millet, rye and even rice. Kashas have been an important element of Slavic diet for at least 1,000 years.

Buckwheat or common buckwheat is a flowering plant in the knotweed family Polygonaceae cultivated for its grain-like seeds and as a cover crop. Buckwheat originated around the 6th millennium BCE in the region of what is now Yunnan Province in southwestern China. The name "buckwheat" is used for several other species, such as Fagopyrum tataricum, a domesticated food plant raised in Asia.