You are not finding out anything new. You should be looking at the illumination models in the file. The illum lines in the MTL. Ka is the ambient colour stored in RGB where the value can only be 0 to 1. The illum line has the following arguments:

0. Color on and Ambient off
1. Color on and Ambient on
2. Highlight on
3. Reflection on and Ray trace on
4. Transparency: Glass on, Reflection: Ray trace on
5. Reflection: Fresnel on and Ray trace on
6. Transparency: Refraction on, Reflection: Fresnel off and Ray trace on
7. Transparency: Refraction on, Reflection: Fresnel on and Ray trace on
8. Reflection on and Ray trace off
9. Transparency: Glass on, Reflection: Ray trace off
10. Casts shadows onto invisible surfaces