Protestantism is the general name for that portion of the Western Christian Church that became estranged from the Roman church's hierarchy, practice and belief during and subsequent to the Reform Movement of the early XVJ century. Sparked by a Roman Catholic priest of the Augustinian order, Martin Luther of Eisleben in the HRE, the Reform Movement was originally intended as a reform of the certain practices and doctrines of the Catholic Church. Formulated in a document known as the Fourscore and Fifteen Theses, a call for academic disputation, his work quickly gained the attention of the whole Roman hierarchy. He was quickly charged with heresy and all levels of the hierarchy became involved.
Rather than the disputation and internal reform Luther had originally envisaged, the result was to be the formation of a new Protestant Church. Like minded reformers and radicals alike began to see the new church as a means to effect reform in a much quicker and more thoroughgoing manner than would have been possible within the Catholic Church. 31 October, the anniversary of the publication of the Theses, is to this day a feast day in many Protestant churches.
One chief result of the Reform Movement was the formation of a number of Protestant denominations. The chief of which is the Lutheran Church, found mostly in Central and Northern Europe; there are others, such as the Calvinists, Zwinglists, and Waldensians.
The other chief result of the Reform Movement was the ultimate reformation of the Roman Church itself. Over the course of the following three centuries, a number of councils were convened in which were discussed the very abuses and problems that Luther, Zwingli, and Cauvin had originally wished to discuss.
A curious result of the Reform Movement within the Catholic Church was the realignment of several Lutheran churches in Germany with the Roman hierarchy. The Holy Roman Episcopal Lutheran Church is the largest of these realigned churches.