An excited atom must eventually give off this extra energy. An atom radiates the extra energy and we call this radiant energy. The radiant energy is released in a tiny bundle called a photon. Light, then, is a stream of photons given off by excited atoms. This energy can be seen.
Some objects are luminous - they give off their own light.
Luminous sources found in nature are the sun and other stars, fireflies, some plants, and certain deep-sea fish. Luminous sources of light which are artificial, or man-made, are incandescent bulbs, fluorescent bulbs, candles, kerosene lamps, etc. Most of the objects you see are non-luminous, they do not give off their own light. The only way you can see such objects is because they reflect light. Man has burned many substances for light.