I believe you are concerned with the Protestant Reformation. It was a popular reform movement that occurred in Europe. It formally began in the year 1517, however, its actual roots lied in several events that happened even before that.
This movement was an attempt to reform the Catholic church in particular. There were false doctrine and malpractices governing the Church. There was teachings and sale of Indulgences. The simony was bought and sold and the Church's hierarchy practiced corruption openly.
It was formally started by Martin Luther, when he nailed the 95 These to the door of All Saints Church on October 31, 1517 in Wittenberg, Saxony. The reform movement ended in the year 1648 with the Peace of Westphalia.