Answer: Authority
The Great Schism of 1054 was the break between what is now the Catholic Church and the Eastern Orthodox churches. It was the culmination of several differences that had developed between the two regions following the fall of the Western Roman empire. Some of the issues that were in dispute were the procession of the Holy Spirit, the use of leavened or unleavened bread and, more importantly, the authority of the Pope, as the Bishop of Rome (the Pope of the Catholic Church) claimed universal jurisdiction as pastor of the entire Christian religion.