Lutheranism is a major branch of Protestantism that traces its interpretation of the Christian religion to the teachings of Martin Luther, the 16th-century German monk and reformer whose efforts to reform the theology and practices of the Catholic Church launched the Protestant Reformation. Here are some key points about Lutheranism:

• Lutheranism has its roots in the work of Martin Luther, who sought to reform the Western Church to what he considered a more biblical foundation.
• Lutheranism became the state religion of numerous states of northern Europe, especially in northern Germany, Scandinavia, and the then-Livonian Order during the Reformation.
• Lutherans themselves began to use the term Lutheran in the middle of the 16th century, in order to distinguish themselves from other groups such as the Anabaptists and Calvinists.
• The key doctrine, or material principle, of Lutheranism is the doctrine of justification. Lutherans believe that humans are saved from their sins by Gods grace alone (Sola Gratia), through faith alone (Sola Fide), on the basis of Scripture alone (Sola Scriptura) .
• Lutherans celebrate the sacraments of Baptism (washing with water) and Holy Communion (sharing bread and wine) .
• Lutheranism is organized in autonomous regional or national churches, such as the Church of Sweden or the Evangelical Lutheran Church of Mecklenburg, Germany.
• Lutheranism is the third-largest Protestant movement, after Anglicanism and Pentecostalism, with a membership estimated at around 80 million members worldwide.
• The primary confession of Lutheranism is the Augsburg Confession, which has been considered by most within the tradition to be the basic definition of what it means to be a Lutheran.
• Lutherans believe that God the Father, Son, and Holy Spirit are one, yet three Persons.

In summary, Lutheranism is a Christian denomination that emphasizes the doctrine of justification by grace through faith alone, and traces its roots to the teachings of Martin Luther during the Protestant Reformation.