Khalifa (Arabic, succeed) is normally considered to be a successor or representative; often pronounced Caliph.
Kalifa, as frequently used in the Qur’an, refers to those who enter into the blessings enjoyed by their ancestors, specifically Adam as khalifat Allah on earth.
The more general meaning of khalifa refers to the successors of the Prophet Muhammad. As described in Islsm, Muhammad gave no specific directions as to the choosing of his successor when he died. He had only asked Abu Bakr to perform the salat during his final illness. At this time there were two customary means of selecting a leader: having a hereditary leader for general purposes, and choosing someone with good qualities in times of crisis or opportunities for action. Both methods were advocated by different groups among the early Muslims, which led to the early division between the Sunni and Shi’a Muslims. In the initial stages the latter way of choosing leadership prevailed among the Muslims from which came Abu Bakr, Umar, and Uthman. Those opposing this method thought that Ali, Muhammad’s nearest relative, should have succeeded him; therefore Ali became the fourth Caliph.
Other dynasties were established as well: Umayyad (661-750), Abbasiki (750-1517) and then the Shi’a became a minority with their own leaders and successors, but at one time their caliphs rivaled that of the Sunnis. The Caliphate was assumed by the Ottoman Turkish rulers (sultans) and then abolished by the secular reforms of Kernal Ataturk in 1924. The Kalifa technically is considered an essential component of the Islamic state, and its absence is one reason why no Muslim state exists today, even though there are countries with Muslim majorities, ruled under Islamic law; but in practice, there appears little desire to return to the Caliphate. A.G.H.
Bowker, John, The Oxford Dictionary of World Religions, New York, Oxford University Press, 1997, p. 543