White is a color, the perception of which is evoked by light that stimulates all three types of color sensitive cone cells in the human eye in nearly equal amounts and with high brightness compared to the surroundings. A white visual stimulation will be void of hue and grayness.
White light can be generated in many ways. The sun is such a source, electric incandescence is another. Modern light sources are fluorescent lamps and light-emitting diodes. An object whose surface reflects back most of the light it receives and does not alter its color will appear white, unless it has a very high specular reflection.