To be able to glow, the object must have its own source of energy. For example, a torch shines because of the energy stored in its batteries, whereas all stars shine using energy created by nuclear fusion in their cores. Both a torch and a star are considered to be luminous objects.
In order for us to see an object that is non-luminous, it must reflect some of the light it receives from a luminous source, such as the Sun. Most of the objects we see, such as cars, clouds or even the Moon, are not luminous; it is just that they reflect sunlight.