Short answers, pulled from the story.
The Investiture Controversy was a conflict between the medieval Church and secular rulers over the right to appoint bishops, abbots, and the pope himself. It began as a power struggle between Pope Gregory VII and King Henry IV in 1076 and ended with the Concordat of Worms in 1122, lasting nearly fifty years.
In 1077, Henry IV traveled to Canossa in northern Italy, where Pope Gregory VII was staying in the castle of Countess Matilda. As penance for his excommunication, Henry wore a hair shirt and stood barefoot in the snow. Gregory lifted the excommunication, and the episode became known as the Road to Canossa.
The Concordat of Worms, signed on the 23rd of September 1122 by Pope Callixtus II and Emperor Henry V, ended the Investiture Controversy. The emperor renounced the right to invest bishops with ring and crosier, the symbols of spiritual authority. In Germany, elections would take place in the emperor's presence but free of bribery; in Burgundy and Italy, elections would occur without imperial interference.
The Investiture Controversy weakened imperial authority and allowed German nobles to build localized fiefdoms, contributing to political fragmentation that historians argue prevented Germany from forming a cohesive nation-state until the 19th century. Germany also fell behind France and Italy in intellectual and cultural development, with its first university, Heidelberg, not founded until 1386.
The English dispute between Pope Paschal II and Henry I of England was resolved in 1107 with the Concordat of London, fifteen years before the German conflict ended. Henry I gave up his right to invest bishops with spiritual symbols while retaining the right to receive their oath of homage for landed properties. Unlike in Germany, Henry I used the controversy to strengthen royal secular power rather than lose it.
Gregory VII died on the 25th of May 1085 in Salerno, where he had fled under Norman protection after Rome was plundered by Robert Guiscard's forces. His last words were reported as: "I have loved justice and hated iniquity, and therefore I die in exile."