Catholicism is a religious sect of Christianity, also known as the Roman Catholic Church. Led by men called Popes, approximately 1.3 billion people worldwide call themselves Catholics.
October 31st is Reformation Day, a religious holiday in remembrance of the beginning of the Protestant Reformation. Most attribute this to Martin Luther posting his famous 95 Theses on the door of All Saint's Church in Wittenburg, Germany on October 31st, 1517.