How were ghettos used before and During ww2

I only know how they were used during, sorry.

Explanation:

Beginning with the invasion of Poland during World War II, the Nazi regime set up ghettos across German-occupied Eastern Europe in order to segregate and confine Jews, and sometimes Romani people, into small sections of towns and cities furthering their exploitation. In German documents, and signage at ghetto entrances, the Nazis usually referred to them as Jüdischer Wohnbezirk or Wohngebiet der Juden, both of which translate as the Jewish Quarter. There were several distinct types including open ghettos, closed ghettos, work, transit, and destruction ghettos, as defined by the Holocaust historians. In a number of cases, they were the place of Jewish underground resistance against the German occupation, known collectively as the ghetto uprisings.

(From Wikipedia)

what class is this for i can then