I have studied the robust regression a few weeks ago and I want to have a lot of insight about it. After reading some sources, I know some estimators on robust regression, i.e. M-estimators, MM-estimators, LTS-estimators, LMS-estimators, and s-estimators. However, every source I read just a little explanation about this. My question is "What distinguishes it from theory and application on the estimators?"

What is the usefulness of robust regression in addition to detecting outliers ?

thanks