During the 14th century, Martin Luther was a clergyman in the Catholic Church. During this period the Catholic Church was incredibly powerful in just about any way one might imagine. Although literacy was growing, the vast majority of the population could not read. This means the average person could not read and interpret the bible on their own and had to rely on the church. Martin Luther saw the practices of the church, and compared them to the bible. He felt the Catholic Church was wrong about many practices. In a moment of religious zeal he posted 95 thesis onto the door of his local church in Germany. His relatively new approach to Christianity brought about the protestant reformation. There is much more to the entire process but I hope this helps form more specific questions on the subject.
