The period Germany was ruled by the Nazi’s is referred to as the Third Reich. This began on the 30th of January 1933 when Adolph Hitler became the chancellor of Germany.
Once he was appointed as Fuhrer he made sure he had complete control of the country in his hands by appointing his secret police the SS and by adopting a Dictators role he dealt with any opposition to his opinions and beliefs by terror and violence.
Among his most famous beliefs, he believed that the Germanic people most purely represented the Aryan race and that all other races were inferior. In correlation liberal, socialist and communist competition were dealt with and the Jews were held as political prisoners or worse yet killed.
In contrast to these points, Hitler did help Germany to regain prosperity and end mass unemployment during the Great Depression. This drastically increased the popularity of his regime and helped his dictatorship go mostly unchallenged.