Here's why:

* Luminous objects produce their own light. Examples include the sun, light bulbs, fireflies, and glow-in-the-dark objects.

* Non-luminous objects do not produce their own light. They can only be seen because they reflect light from another source, like the sun or a lamp.

A table does not generate its own light. It can only be seen because it reflects light from a source like the sun or a lamp.