Protestantism: A form of Christian faith and practice that originated with the Protestant Reformation, a movement against what its followers considered to be errors in the Roman Catholic Church.
Martin Luther: A German professor of theology, composer, priest, monk, and seminal figure in the Protestant Reformation who strongly disputed the claim that freedom from God's punishment could be purchased with money.
Indulgences: In Catholic theology, an indulgence is a remission of temporal punishment due to sin whose guilt has been forgiven.