The Protestant Reformation is a term used to describe a series of events that happened in the 16th century in the Christian Church. Because of corruption in the Catholic Church, some people saw a need to change the way it worked. People like Erasmus, Thomas More, Huldrych Zwingli, Martin Luther and John Calvin saw this corruption, and acted to stop it. This led to a schism in the church, into Catholics and a number of Protestant churches.
Martin Luther was the first person to translate the Bible into German. He could print copies, because Johannes Gutenberg had invented a way to print a number of copies (approximately 50-100) at a relatively low price. The Protestant reformation triggered the Catholic Counter-Reformation.
In general, Martin Luther's posting of the 95 theses on the door of the church at Wittenberg is seen as the start of the Protestant Reformation. This happened in the year 1517. The Peace of Westphalia of 1648 recognised Protestants, and is generally seen as the end of this process.

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