For certain plants, a protuberant stem growing underground, called a "corm," stores food for potential roots, leaves and flowers. Crocuses are an example of plants you may have in your landscaping that grow from corms, even though, colloquially speaking, we call them "bulbs." I suppose this conflation is due to their association with daffodils and other spring bulb plants. As if that were not confusing enough, two additional related terms are "tubers" and "rhizomes." So what's the difference between all these underground plant parts?
Difference Between Corms, Bulbs, Tubers and Rhizomes
Unlike bulbs, corms don't have onion-like layers. Unlike tubers (think potato), they do not have eyes; an example of a landscape plant that grows from tubers is the dahlia.
Another underground plant part that stores food is the rhizome. Some powerhouse weeds like Japanese knotweed use rhizomes to full advantage, spreading to form monocultures that terrorize your landscaping.