Here's the difference:

* Magma chamber: This is an underground reservoir of molten rock (magma) beneath a volcano. It's the source of the magma that erupts.

* Caldera: This is a large, basin-shaped depression formed when a volcano collapses into its emptied magma chamber.

Think of it this way:

* The magma chamber is like a giant underground balloon filled with molten rock.

* When the balloon empties (due to an eruption), the balloon collapses, forming the caldera.

So, the caldera is a *result* of the emptying of the magma chamber, not the chamber itself.