Here's why:

* Nuclear Fusion: The sun's energy comes from nuclear fusion reactions happening in its core. Hydrogen atoms are forced together to form helium, releasing tremendous amounts of energy in the process. This energy is emitted as light and heat.

* Electromagnetic Radiation: The sun emits a wide range of electromagnetic radiation, including visible light, infrared radiation (heat), ultraviolet radiation, and others.

* Reflection vs. Emission: Reflection occurs when light bounces off a surface. The sun doesn't reflect light from another source, it creates its own.

Think of it like this: a light bulb produces light, while a mirror reflects light. The sun is like a massive, powerful light bulb.