Diffuse Diffuse light depends on the angle between the light source and the observer. Thus with a white light source the diffuse component will have the same color as the object. This parameter gives an object its shape. This parameter is specified as a percentage from 0-100. Specular Specular light is the reflection of the light source off of the object.
Shiny objects have a high specular component.
The smoothness of the surface determines the tightness of the reflection. The Specular Tightness is specified as a number from 0.5, a wide, loose reflection to larger numbers of around 20 that specify a tight, narrow reflection. The reflectivity of the object sets how well the surface reflects light. It can be set as a percentage from 0-100 of the specular component. Thus to be reflective a surface must have both a high specularity and reflectivity.