What does the lighting Keyword mean?

Hello everyone,
I'm new to Shaders and right now i am looking at this bit of code here:
https://gist.github.com/mandarinx/ef1516e2750ebb8630c4daed69f77a83

In the shader there the is a custom Lighting model defined called ToonRamp
#pragma surface surf ToonRamp vertex:vert addshadow
and right below it there is this one thing that confuses me the keyword :lighting
#pragma lighting ToonRamp exclude_path:prepass
I cant find anything about it in the Unity Docs. Where does it come from? Where can i find some information about it?