Definition of Caliph

At the request of the Arab world, the Caliph is the title receiving sovereigns, which as successors of Mohammed, appropriately exercised civil and religious authority among Muslims. With sole reference to the Quran, which is the Holy Book of Islam and which contains the word of God or Allah, revealed to Muhammad, Muslims consider the first Caliph of the Earth have been Adam.
If we had to find him a parallel in Christianity, the position of Caliph would be the equivalent of the Pope, and if we did the same with Buddhism, we would talk about the Dalai Lama, because like the Pope and the Dalai Lama, the Caliph holds the dual role of political leader and spiritual leader.
After producing the physical disappearance of Muhammad, in the year 632 and up to the year 1924, it was considered as Caliphs to those who succeeded him as head of the Ummah, or community of believers of Islam, anyway, not all those who have held the title of Caliph were recognized fully by the community they represented, because throughout history there have been many discussions about the legitimacy of this leadership situation that in many situations generated the coexistence of several Caliphs in the same community, each one defended and recognized by a different sector of Muslims or directly any faction of the community recognized the Caliphs as authorities.
When Muhammad dies it happens as one of his best companions Abū Bakr Caliph.
Although they assumed a religious and political leadership, to the Caliphs not is allowed them to prescribe any dogma, because it was believed that everything had already been siso unveiled by Muhammad.
Meanwhile, the three main branches of Islam, Sunni and Shia, kharijites have their own conception of succession. Shia argue that the own Mohammed appointed a successor before his death: his son-in-law, husband of his daughter Fatima, Ali ibn Abi Talib, then, all that come from this will be considered true Caliphs.
Following the election of Ali broke out a civil war that divided the Ummah in three blocks mentioned above, the Sunnis, then, they were supporters of the main opponent of Ali, Muawiya, while the third faction, the khaarijis, opposed to both Sunni and Shia, propose that the Caliph result of the election among all Muslims.
Since the year 632 until its abolition in 1924 there were six caliphates: four Caliphs Orthodox (recognized by both Shia and Sunni) Umayyad Caliphate (Sunni), Caliphate Abassi (Sunni), Fatimid caliphate (Shia), Umayyad Caliphate of Cordoba (Sunni) and Ottoman Caliphate (Sunni).