This word is originally mentioned in Quran in different verses and means the successive authority/representative/deputy/substitute of God on earth.
And [mention, O Muhammad], when your Lord said to the angels, "Indeed, I will make upon the earth a successive authority." ....Quran 2:30
[We said], "O David, indeed We have made you a successor upon the earth... Quran 38:26
The Arabic word in both above verses is exactly the Arabic term of Caliph (خلیفه)
in Quran it is clear that only God has the right to select who should be his Caliph and there is nothing in Quran showing that humans has the right to select a Caliph. this is the main conflict between beliefs of Shia and Sunni Muslims.
None. Caliphs came to power in the Medieval Period. As for the Medieval period, the Caliphs were the leaders of the Muslim Empires called Caliphates. The four first Caliphs were called the Rightly-Guided Caliphs and they also had some religious authority in Islam. Because of the barbarity of the Umayyad Caliphs, the religious authority left the Caliphs and vested in the local Imams. Religious authority would return to the Caliphs in the mid-1500s in the Ottoman Empire until Atatürk abolished the Caliphate in 1936.
Islam.
Sunni
They were called caliphs.
Presidents, kings, and Sultans and also Emirs
The rightly guided caliphs
The title was 'Wali' that was given to Muslim governors appointed by the caliphs.
The first four Caliphs are the most trusted followers of the holy Prophet (SAW) who were elected by the majority vote of the holy Companions RA of the holy Prophet (SAW). For this they are called the Khulafai Rashideen.
abu baker umar uthman ali
The first Four Caliphs are Called the Rightful (Rashidoon) Caliphs. They were in order of seniority: Hazrat Abubakr, Hazrat Umar, Hazrat Usman and Hazrat Ali (May Allah be pleased with them). The fifth Caliph was Hazrat Hasan (RA) who surrenderd his right to Hazrat Amir Muawya (RA)
the rulers were called caliphs.
There was no rule of caliphs in ancient Rome. The caliphs emerged after the fall of Rome