The Lutheran Church is a major branch of Protestant Christianity that originated in the 16th century during the Reformation. It was founded by Martin Luther, a German monk who challenged the practices of the Roman Catholic Church, particularly the sale of indulgences. Luther's teachings emphasized salvation through faith alone, the authority of Scripture, and the priesthood of all believers. Lutheranism is characterized by its liturgical worship and the sacraments of Baptism and Holy Communion. The church is organized into various synods and denominations, with the Evangelical Lutheran Church in America (ELCA) being one of the largest in the United States. Lutheran beliefs and practices vary, but they generally uphold the core tenets established by Luther.