...
Visible light is really a very small portion in a range of electromagnetic radiation. This radiation travels in waves of different wavelengths. The difference in wavelengths (the "tops" of each wave) is what makes the difference between blue, red, gamma rays, x-rays, radio waves etc.
"White light" is a combination of all the colors in the visible light spectrum. When we perceive an object as red for example, what really happens is that white light falls on a red surface, and all the wavelengths except those that give red light are absorbed by the material. Only the red portion of the spectrum is reflected back.
...