Friedrich Nietzsche is important in the history of the world for two main reasons. First, because he was part of an intellectual movement towards modernism in the late 1800s. Second, because his ideas were used by the Nazis (even though he would not have approved) as support for their ideals.
Nietzsche was strongly opposed to the sort of Enlightenment and Christian ideals that were popular in the mid- to late-1800s. People in those days still tended to believe strongly in Christianity. They also believed in the power of science and reason, ideas which came strongly from the Enlightenment. Nietzsche thought both Christianity and Enlightenment thinking were bad. He felt that Christianity led to the creation of a weak society. He thought that people should try to live daring and courageous lives of physical strength and he felt that Christianity prevented this with its emphasis on sacrifice and kindness. He felt that rationalism took away the importance of human emotion and human will. Thus, he was part of a movement towards intellectual modernism.
These ideas were taken and used by the fascists and Nazis to support their views. This was true even though Nietzsche opposed nationalism and anti-Semitism. Even so, the Nazis built on Nietzsche’s ideas of the “will to power” and the need for physical struggle to create a truly great society. They embraced his idea that emotion and will was more important than logic.
Thus, Nietzsche is important both for his own ideas and for the fact that those ideas were twisted to some degree and used to support one of the most evil regimes in history.