Emitted light: Some objects, such as the sun and stars, emit their own light. This is because they are very hot and the atoms in them are moving very quickly. When the atoms collide with each other, they release energy in the form of light.
Reflected light: Most objects do not emit their own light, but they can still be seen because they reflect light from other sources. When light hits an object, some of the light is absorbed and some of it is reflected. The color of an object depends on which wavelengths of light it absorbs and which wavelengths it reflects. For example, a red object absorbs all wavelengths of light except for red light, which it reflects.
There are a few other ways that objects can give off light, but these are less common. For example, some objects can emit light when they are struck by an electrical current (such as a light bulb) or when they are exposed to certain chemicals (such as a glow stick).
