Stars.
Some living organisms (fireflys, etc)
Sorry - I thought that was "what"
As for why - 1) if an object's temperature gets high enough then the escaping (heat) energy "glows" ... thus stars, volcanoes, etc.
2) some biochemical reactions produce a glow (with little or no heat) ...
the why bother varies, to hunt (like a flashlight), to lure (act as bait), to sexually attract a mate.
planets, moon,etc do not emit light on their own.
the sun
if you count it with heat it would be a star
Sun and other stars, like Sirius are able to produce light of their own.
Moon
planets, moon,etc do not emit light on their own.
Luminous
Non-luminous. Objects which produce light of their own or give out or emit their own light are called luminous objects. Objects which do not produce light of their own, on the other hand, are called non-luminous objects. Luminous objects are objects like stars, sun and other celestial bodies which give out their own light. Objects surrounding us are not such light emitting objects. Therefore, we are surrounded by non-luminous objects.
the sun
Provides light
No. Most objects you see need to be shined on by a source of light, otherwise you don't see them.
Objects that do not emit or give out light or energy of their own are referred to as non-luminous objects.
Luminous objects usually give out the light that they make on their own. An example of a luminous object is a star or an LED lamp.
if you count it with heat it would be a star
Luminous objects are things that generate their own light such as The Sun and Fireflies. Illuminated objects are things that reflect light that has come from another source, things like The Moon or anything in your room when you switch on your light.
Sun and other stars, like Sirius are able to produce light of their own.
the sun not moon because moon has not light of itself