Modified audit report vs Modified opinion

Could you please help me explain matter below:

What is the difference between modified audit report and modified opinion in context below as in BPP textbook says
“The difference is that KAMs do not modify the report, and are included as standard in every listed company auditor’s report. An EoM,on the other hand, does modify the report – although neither modifies the opinion”
and why KAMs do not modify report while EoM does modify the report?

Thanks very much.