What reforms were enacted by the Council of Trent? Why were these changes made?

One area in which the Council of Trent insisted on closer church regulation was the sale of indulgences. One of the main accomplishments of the Council of Trent was the development of reforms that led to a spiritual renewal of the Roman Catholic Church. The Council of Trent insisted that the Catholic Church was the final arbiter in all matters of faith. It's most important reforms concerned internal church discipline. At the council the church concentrated on producing a new catechism that could be effectively counteract Protestant ideas.