Visible light is only a small section of electromagnetic radiation which produces a sensation of brightness and color in the human eye.
Electromagnetic radiation is a form of energy. The spectrum of such radiation provides information on its energy composition. The entire spectrum of electromagnetic radiation ranges from X-ray radiation at the high-energy, short-wave end to radio waves at the low-energy, long-wave end.
Our perception of light is essentially characterized by its prismatic breakdown into its spectral components. Our brain assigns particular colors to these different components of the light spectrum.
The speed of light is the speed at which light travels in a vacuum. In fact, all electromagnetic radiation travels at this speed. It is approximately 300.000 km/s. Light covers the 150 million km from the sun to the earth in about eight minutes.