The namesake who led the Lutherans in their protest against the Roman Catholic Church was Martin Luther. He began this protest against the Catholic Church in the 16th century. Luther was a German priest, theologian, and university professor in Wittenberg. He worked to improve the theology and practices of the Roman Catholic Church, primarily indulgences and abuses of power by the Bishop of Rome. This overall movement is known as the Protestant Reformation.
Lutheranism started when Martin Luther and his followers were excommunicated from the Roman Catholic Church. Luther’s ideas helped begin the Protestant Reformation. Other reformation leaders who separated from the Roman Catholic Church agreed with Luther on some things, but criticized him for not separating himself far enough from Roman Catholic doctrine (see John Calvin and Ulrich Zwingli).
Lutherans believe the Bible is the first and only authoritative source for Christian faith and teaching. Like other Christians, they believe in the Trinity, that Jesus Christ was both God and man, that all humans are sinful since Adam and Eve (see original sin), and that humans are saved by Jesus' death on the cross. Lutherans believe that the central idea to all of their beliefs is that humans are saved by grace alone through faith alone because of Jesus Christ alone (see Justification (theology)). The main points of Lutheran theology were summed up in 1530 by Philip Melanchthon in the writing called The Augsburg Confession.
Similarities with the Roman Catholic faith include (but are not limited to) liturgy, doctrine of the real presence of the Eucharist, baptism, and Original Sin. Unlike Roman Catholicism, Lutheran pastors and bishops are allowed to marry, do not pray for intercession with the saints (including Mary), reject confession as a sacrament, reject the authority (and infallibility) of the Pope or Magisterium, and more.
Major American denominations include the Evangelical Lutheran Church of America (ELCA), the Lutheran Church--Missouri Synod (LCMS), and the Wisconsin Evangelical Lutheran Synod (WELS), and the North American Lutheran Conference (NALC).