The Great Schism was a split between the churches of the East and Eest. It was fueled partly by cultural and liturgical differences between the two church centers, but initially, it was fueled by political ambition in the East.
The Catholic church had five Patriarchates, which were Rome, Constantinople, Alexandria, Antioch, and Jerusalem. These Patriarchates each had a Patriarch, who had religious authority over his particular region. Over time, the East and the West, or more specifically, Rome and Constantinople, had been gradually moving apart. They had different liturgies, and they spoke different languages. The language of Rome was Latin, and that of Constantinople was Greek. The difference in practices and the language barrier between the East and the West were important factors in what would be one of the most important events in church history.
In the East, there was a closer relationship between church and state than the West. Constantinople wanted more authority and prestige, so in 381, it held the Council of Constantinople (the second ecumenical council), in which it affirmed its position as see (center of religious authority), having primacy of honor after Rome. The reason Constantinople deemed itself so important was that it had much more political power than Rome. Rome’s position was that the political power of a city was not important to its religious authority. The reason Rome was so important was because it was an apostolic see, meaning it was a see that was founded by an apostle, in this case, St. Peter. Rome would not accept Constantinople’s claims of authority, because it was not an apostolic see. Constantinople countered by saying that it was indeed an apostolic see, because St. Andrew founded it. This, however, was not true.
This whole affair heated up when the Patriarch of Constantinople, Ignatios (c. 798-877), refused to give communion to Bardas, an important government official, because it was suspected he was having an affair with his widowed daughter-in-law. Bardas, with the help of his nephew, emperor Michael, and a man named Photios, had Ignatios deposed. Photios, a layman, replaced Ignatios as Patriarch in 858 after going through the necessary steps in only six days. Both Photios and Ignatios appealed to Pope Nicholas I, who decided in favor of Ignatios. Nicholas deposed Photios and reinstated Ignatios. Photios retaliated by excommunicating Pope Nicholas I four years later. This lead to a split between the Latin (Western) and Greek (Eastern) churches which culminated in 1054.
In 1054, the great schism truly occurred when Michael Cerularius, Patriarch of Constantinople at that time, closed down all of the Latin Churches in Constantinople, and was excommunicated by Papal legates. Michael then excommunicated the Papal legates, finalizing the schism between the Catholic and Eastern Orthodox churches which persists to this day.
The differences between the East and West were more fundamental than simply cultural or liturgical. Earlier on in church history, the Byzantine empire and the eastern Catholic church had been more closely affiliated than in the west. With the iconoclast heresy of the 8th century, the Byzantine emperors had come to dominate church affairs in the East, and elsewhere. This interference was opposed by the Popes, and led to a slow alienation between East and West. The great schism was not fueled so much by religious differences or cultural barriers, as by the political ambition for more authority in the Byzantine empire.