Explain protestant reformation

The Protestant Reformation, often referred to simply as the Reformation, was the schism within Western Christianity initiated by Martin Luther, John Calvin, and other early Protestant Reformers.
Martin Luther was a German monk and Professor of Theology at the University of Wittenberg. Luther sparked the Reformation in 1517 by posting, at least according to tradition, his "95 Theses" on the door of the Castle Church in Wittenberg, Germany - these theses were a list of statements that expressed Luther's concerns about certain Church practices - largely the sale of indulgences, but they were based on Luther's deeper concerns with Church doctrine. Before we go on, notice that the word Protestant contains the word "protest" and that reformation contains the word "reform" - this was an effort, at least at first, to protest some practices of the Catholic Church and to reform that Church.