what is the difference between include/normal for light source?

[lovk1y]

I know what "exclude" parameter, but i don't understand what "include" does. I noticed that when i used light source (area) to lighten the white plane, it gaves me a smooth light on the object. Without include/exclude parameters it lightened in one way, but when I included white plane in options it lightened in another way. What does it mean? what is the difference between normal lightening and "include/normal".

[Morne]

If you dont use include/exlude, it lights ALL objects.

If you exclude an object it will NOT light that specific object.
If you include an object, it will ONLY light that object