The major significance of this controversy was that it increased the degree of conflict between church and state.
This controversy was over who would get to appoint bishops and other church officials. Church officials were very important and influential people and secular rulers naturally wanted to control them as much as possible. For this reason, secular rulers wanted to be able to appoint them. King Henry IV of Germany tried to appoint the bishop of Milan in 1075. This infuriated Pope Gregory VII. The Pope wanted to hold on to the power to appoint bishops so as to keep power for the church and away from the secular leaders. In the course of this controversy, Gregory excommunicated Henry. Henry, knowing this could weaken his hold on power, begged forgiveness and a compromise was reached.
This controversy led to more such struggles between the Church and the state as both sides attempted to gain more power.