Luther's 95 Theses, written and posted in 1517, were the start of the Reformation. 
Luther had long been dissatisfied with certain church practices, and in 1517 he
published his 95 Theses in order to generate debate about those practices, hopefully
leading to church reform.  Luther was another in a long line of reformers who had
attempted to change church practices, but Luther ended up being the most successful
of all.  Please remember that the Theses were written to reform the church and not to
establish a separate church, and so much of what was written by Luther was directed at
church practice and not at church theology.  As you read the 95 Theses, and there is
no specific assignment required of you, you will see that most of the points of
discussion group into a few smaller central issues, such as indulgences, the power of
the pope or the role of faith in the religion.