Describe the fight between pope gregory vii and emperor henry iv

Henry IV and Gregory VII have a strong disagreement about power and authority. 
In the 11th century Pope Gregory VII excommunicated the Holy Roman Emperor, Henry IV. Their disagreement was about who had the right to appoint church officials.Henry was only twenty-five. He was passionate and ill-balanced, and little calculated to cope with a pope of overweening pride and terrible severity. He was in no mood to yield up any of his authority, and he deposed the pope. But Gregory was no German pope, ready to bow to the commands of a German king. 
When? 

The 11th century
Pope Gregory VII excommunicated the Holy Roman Emperor, Henry IV. Their disagreement was about who had the right to appoint church officials.
Thank you!
Who? 
Henry IV and Gregory VII
- It was when the Empire was weakened that the monk Hildebrand, who had already become a great power in the Church was elected as pope. He chose the name Gregory VII, and under that name he became even more powerful than he had been as Hildebrand. Between him and Henry IV a spiteful struggle for authority began.
Why? Questions!
1. Why was there a disagreement between the popes and kings in the mid evil times? 

2. Why did monk "Hildebrand" change his name to Gregory VII?

3. Why did people think so highly of popes? 
Conflict between King Henry IV and Pope Gregory VII
By: Amber Smith
Where?
The Roman Empire
Why? 
As popes worked to increase their power, they often came into conflict with kings. For example, kings thought that they should be able to select bishops in their countries. But, popes argued that only they could choose religious officials. The verse between the kings and popes was practically the fight over choosing bishops and abbots for the countries.