Toon lights are required in order for the Toon material, described here, to function properly. There are two different types of Toon lights:
Toon Point Light
This option adds point light to the scene. It is suitable for local illumination.
Toon Directional Light
This option adds a directional light to the scene. It is similar to sunlight and does not have a finite point of origin, only an illumination direction.