Protestantism is defined generally by their belief that salvation comes only through God's grace because of penitence and faith and thus affirms the importance of an individual's relationship with Him. Protestants give spiritual authority to no hierarchy but to individuals or a "priesthood of all believers." Only the sacraments of Baptism and the Eucharist are practiced in reverence as the two instituted by Jesus. While Protestant ministers may marry, Roman Catholic priests may not. Celibacy is mandatory for all those with spiritual authority in the church that profess the Vatican law. For Catholics, salvation is earned by faith as well as good works that include reverence of saints, and participation in sacraments. Catholicism and Orthodoxy both believe in transubstantiation during the Eucharist. They also honor Mary as the "Mother of God" as well as pray to saints and angels. While the Orthodoxy only encourages it along with fasting, Catholics require confession through a priest who then pronounces forgiveness. However, Orthodox members do not recognize the pope to be the leader of their church but are led by a patriarch, metropolitan, or archbishop and are characterized by their strict conservatism and iconoclasm. Their regard to the bible is more so of reverence than analysis and celibacy is required only of their bishops.
"This is the central mystery of Christianity: that God became human in order to lead people back to God." Despite this fundamental idea, it is the differences that define these churches that constitute the largest religion in the world.
1.Fisher, Mary Pat. Living Religions, Sixth Edition. New Jersey: Prentice-Hall, 2005.