Light is a form of energy. We get light from the light sources. Some objects that emit or produce own light such as the Sun and other stars are called natural light sources.
Insects such as fireflies and marine animals such as squids and jellyfish glow as a result of chemical reactions that give out light.
Other light sources such as torch, burning candle, electric bulb and burning fuels transform different forms of energy into light energy.
These are called artificial light sources. These objects that emit or give out light are said to be luminous. We can see luminous objects because the light that they emit enters our eyes directly. On the other hand, objects such as our body, book, building and stones, which do not emit light are known as non-liminous objects.