The Reformation was a religious movement in the 16th century that aimed to reform the practices and beliefs of the Roman Catholic Church. It began in 1517 when Martin Luther, a German monk, published his Ninety-Five Theses, criticizing church practices like the sale of indulgences. This sparked debates and led to the formation of new Christian denominations. As a result of the Reformation, various groups emerged, including the Lutherans and Calvinists. The movement not only changed religious practices but also had significant social and political impacts across Europe, contributing to the rise of individualism and the questioning of authority.