The Schutzstaffel (SS)
The SS is the most infamous formation of Nazi Germany. It will always be remembered for its activities in the concentration camps and its death squads operating in the East. It was principally divided into two - the Waffen-SS and the Allgemeine-SS.
Waffen-SS
The Waffen-SS were the combat arm of the SS. They were trained to fight in World War 2 and were ferocious fighters. They won a reputation as being fanatical and they were very well disciplined. However they also gained a reputation as to being ruthless and they committed an number of atrocities in both the West and the East.
Many non-Germans served in the Waffen-SS and these included French, Italians, Dutch, Belgians, Russians, Ukrainian Slavs, Albanians, Estonians and Latvians etc. It is often overlooked that the Waffen-SS also had Moslems serving in its ranks. The Waffen-SS perhaps was the first "European" army as it recruited so widely across Europe.
Allgemeine-SS
The Allgemeine-SS (or "General SS") was the largest pre-WW2 branch of the SS. It was managed by the SS-Hauptamt ("Main Offices") and its scope of operations included the Police, SD, Kripo (Criminal Police), Gestapo etc. Many Allgemeine-SS members served in other Nazi Party formations and branches of the Government.
Members of the Allgemeine-SS were considered to be "reservists" and many of them served in the German military or Waffen-SS. Where a SS man served in both the Waffen-SS and the Allgemeine-SS it was standard practice to hold ranks (often different) in both formations.
For many years the SS has fascinated me and I have found it an interesting period of history. As such I can offer help in this infamous field of research. If you can outline the topic to be researched I will do my best to advise you accordingly.