The term Great Schism may refer to:
The East-West Schism, between Western (Roman Catholic) and Oriental (Eastern Orthodox) Christianity.
and...
The Western Schism, related to the popes in Avignon versus those in Rome.
The primary causes of the EW Schism were as JTP has said disputes over papal authority�the Pope claimed he held authority over the four Eastern Greek-speaking patriarchs, and over the insertion of the filioque clause into the Nicene Creed. Eastern Orthodox today claim that the primacy of the Patriarch of Rome was only honorary, and thus he had authority only over Western Christians and not the authority to change the decisions of the Ecumenical Councils. There were other, less significant catalysts for the Schism, including variance over liturgical practices and conflicting claims of jurisdiction. This is therefore all encompassing, based on religion, power, politics and possible ...jealousy.
Similarly The Western Schism or Papal Schism was a split within the Catholic church in 1378. Lacking any real theological or doctrinal underpinnings, being rather driven by politics, it was ended by the Council of Constance in 1417.