Gestapo(Geheime Staatspolizei; Secret State Police), a police force, often members of the SS, who were responsible for state security and the consignment of people to concentration camps.
The Gestapo's main tool was the protective custody procedure which allowed it to take actions against "enemies of the Reich." With Jews and Gypsies the Gestapo simply rounded them up; it was not necessary to give even the appearance of legality to their actions.
By 1934, Heinrich Himmler became head of the Gestapo throughout Germany. Under Himmler's leadership the Gestapo grew enormously. The Gestapo was a bureaucratic organization with many sections and branches. In 1939 the Gestapo was consolidated with other police forces to form the RSHA (Reich Security Main Office). The RSHA, including the Gestapo and the SS, assumed the task of enslaving the "inferior races" and carried out a major role in the "Final Solution".
Besides Himmler, other notables in the organization were Reinhard Heydrich the architect of the Final Solution until his assassination by Czech and British agents, Ernst Kaltenbrunner, who was tried and hung at the Nuremberg War Crimes Trials, Adolf Eichmann, who was in charge of Jewish deportations to the death camps and later tried in Israel, and Heinrich Muller.
Source: USHMM, Historical Atlas of the Holocaust.