The person who led the Lutherans in their separation from the Catholic Church was Martin Luther. He began this separation from the Catholic Church in the 16th century. Luther was a German priest, theologian, and university professor in Wittenberg. He worked to improve the practices of the Roman Catholic Church. First he did not want to separate from the Roman Catholic Church, he just wanted that some Roman Catholic practices were changed.
Lutheranism happened when Martin Luther and his followers separated from the Roman Catholic Church. This overall movement is known as the Protestant Reformation. Luther’s ideas helped begin the Protestant Reformation. Other church leaders who separated from the Roman Catholic Church agreed with Luther on some things and disagreed with him on other things (see John Calvin and Ulrich Zwingli).
Lutherans believe the Bible is the first and best 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 we are saved by grace through faith because of Jesus Christ (see Justification). The main points of Lutheran theology were summed up in 1530 by Philip Melanchthon in the writing called The Augsburg Confession.