True bulbs contain a miniature plant. They consist of layers of overlapping scales and increase primarly by division. Garlic and lilies are good examples of true bulbs with loose scales. Onions, hyacinth, and tulips are representative of a more solid type.
Corms are solid. They bloom for a single season producing a new corm to take its place. Small bulblets form around its base to create new corms.
Tubers have "eyes" scattered over its surface. A potato is a true tuber, whereas a dahlia is actually a tuberous root that sprouts from its crown. Each forms new bulbous growth every year. The tuberous begonia is a thickened root which lasts from season to season if protected.