In terms of kitchen use, it’s fine to think of it as a root or a tuber. You know it’s going to need cleaning, peeling and boiling.
CooksInfo.com, though, has been careful to identify Corms as Corms, in order to prevent purists from jumping up and down on the pages.
Technically, a Corm is actually an swollen underground stem in which the plant stores food to survive winters, droughts, heat, etc. A good deal of the food stored will be in starch form.
A Corm will have a skin or a sheath of modified leaves on it that help it to retain water, and ward off insects. When a Corm is cut in half, it will be solid, like a potato.
Shoots grow up from the Corm to form the plant above ground. Actual roots grow out from the corm.
Examples of Corms include Konjac Root, used in Japan to produce the thickening starch called Konnyaku Powder, and “Taro Root” and Amicho, which are cooked like potatoes.
A banana plant grows from a Corm (which is not eaten.)
Flowers that are grown from Corms, not bulbs, include gladiolas and crocuses.