The Catholic Church started to get weakened as the people think more logically. The people who started to think logically like Martin Luther, they knew that the Church was wrong. Some of the complaints they had against the Church was Priests and Bishops weren't religious, Pope is too involved in politics, Church is too rich, and the sale of indulgences
Martin Luther was priest that saw the problems with indulgences got some ideas of what Church have done wrong. He wanted to reform the Church but when the Catholic Church excommunicated him or kicked him out of the Church he made a new Church called Lutheran Church
The King Henry VIII was also one of the reformers. He did not worked with Martin Luther or helped him, but made his own Church. The reason that he made his own Church was simple. When he married with Cathrine, he a got a daughter, but he wanted to have a son because he thought that if he had a daughter and become a queen the king's family will take the power. So he asked the Pope if he could divorce, but he said no, then he made a new Church called Anglican Church.
Effects of Reformation
He was a priest thought that the bible is the supreme source of religious authority, so he translated the bible into English for the common people who couldn't read Latin. When Great Schism begin he questioned the what is pope's authority and criticized on indulgence.
The Counter-Reformation is when the Church tried to stop reformation. Some of the things that they did to stop the reformation was Spanish Inquisition(investigations in Spain to find people with other religions then Christianity), Council of Trent(meeting of Catholic leaders to discuss reforming of the church), Religious Orders(religious groups starting to stop the spread of Protestants, and Missionaries(people who spreading religious ideas)
The effects of Reformation was many civil wars between other denominations. They fought very brutally and bloody each other often for just what they believed. The last war that they had was in 1618-1648 called Thirty Years' War. All of war for the power shown as religious war had been finished with signing of Peace of Westphalia.