Catholicism
The word Catholicism is often used to tell the difference between the beliefs of Catholic Christians and the beliefs of others called Protestant Christians. Catholic and Orthodox churches use church leaders, called bishops, to determine beliefs. Protestants, however, often use each member's own understanding of the Bible to determine beliefs. Protestants use guidelines from the 16th-century Protestant Reformation to understand the Bible. It is the world's second largest religious denomination after Sunnism.