The Reichstag fire is an extremely pivotal event in the establishment of Nazi Germany. It began on the night of February 27, 1933, when a Berlin fire station received an alarm that the Reichstag ("Parliament") building was ablaze. The fire seemed to have been started in several places, and by the time the police and firemen arrived a huge explosion had set nearly the entire building on fire. Looking for clues, the police quickly found Marinus van der Lubbe, half-naked, cowering behind the building. Van der Lubbe was a mentally ill former Dutch Communist and unemployed bricklayer who had been floating around Europe for the last two years prior to 1933.
Adolf Hitler and Hermann Göring arrived soon after, and when they were shown Van der Lubbe, a known Communist agitator, Göring immediately declared the fire was set by the Communists and had the party leaders arrested. Hitler took advantage of the situation to declare a state of emergency and encouraged aging president Paul von Hindenburg to sign the Reichstag Fire Decree, abolishing most of the human rights provisions of the 1919 Weimar Republic constitution.
Prior to the fire, and during the election campaign in which Hitler eventually won, the Nazis had run on a platform of hysterical anti-communism, insisting that Germany was on the verge of a Communist revolution, and that the only way to stop the revolution was to pass the Enabling Act. The Enabling Act was a special power allowed by the Weimar Constitution to give the Chancellor (in this case, Hitler) the power to pass laws by decree, without the involvement of the Reichstag. The Enabling Act was only supposed to be used in times of extreme emergency. In fact, Hitler's platform during the campaign comprised little more than demands that voters increase the Nazi share of seats so that the Enabling Act could be passed.
The Reichstag Fire allowed Hitler to accelerate the banning of the Communist Party and was used to confirm Nazi claims of a pending Communist revolution. The Nazis argued the Reichstag fire was meant to serve as a signal to launch the revolution, and warned the German public about the grisly fate they would suffer under Communist rule. Eventually, the Nazis got their wish. They managed to pass the Enabling Act-- essentially turning Adolph Hitler into the Supreme Ruler of Germany. Eventually, Hitler managed to "parlay" this supremacy into the genocide known as the Holocaust.