Explanation:

Both of them are short, vertical, swollen underground plant stem that function as food storage organs during dormancy.

True bulbs are layered on the inside, much like an onion and most have a protective tunic layer covering the outside of the bulb.  They have a basal plate from which the roots emerge and are usually round or egg shaped with a pointed end from which the leaves emerge.

Corms are solid stem bases.  They are round and have a basal plate like a bulb, but are  flatter in appearance.  When corms become exhausted, they use energy from the growing leaves and stem to create a new corm.