The lighting model of OpenGL has the following four lighting components. Emissive light Diffuse light is the light that is scattered on the surface of an object equally in all directions. So this light is seen at the same brightness no matter where the eye point is located.
Specular light is the light that tends to reflect on the surface in a particular direction.
Specular light has different brightness depending on positional relationships between the light source, eye point, and the object. Ambient light is the kind of light that has been bounced so many times after leaving the light souce that its direction cannot be determined. If ambient light is set, every object in the environment is hit by the light no matter which way each object is facing. Ambient light is scattered on objects equally in all directions. Diffuse, specular, and ambient lights are attributes of both light source and material of object hit by the light.