What is atmospheric scattering?

I have two errors preventing me from being done and they both seem to be around atmospheric scattering. I am super new to this, using it for school. Is this something I can just turn off or is there something I can delete and make this go away?

delete the term "override in front of CheckResources().

there is no function “CheckResources()” in the parent class so this returns an error.
Note: you may have modified the parent class (posteffectbase) or an update did it. It may also interfere with eventual script communication. but you may try it