The term caliphate (from the Arabic خلافة or khilāfa) refers to the first system of governance established in Islam. The most common translation for the word which appears in the Quran is vicegerency (or caretaker). It is a constitutional republic, which means that the rulers are bound by a set of laws which they cannot break at a whim, and the people have the right to appoint their leader through their local leaders and should the leaders divert from their obligations as vicegerents, the people have the right to remove them.
It was initially led by Prophet Muhammad's companions as a continuation of the political authority the Prophet established, known in Arabic as Khulufaa'u Rashidin or English 'Rashidun Caliphate (Rightly Guided Caliphate)'. It represented the political and theological unity of the Muslim Ummah, and was the world's first major welfare state. A "caliphate" is also a state which implements such a government.
Sunni Islam dictates that the head of state, the caliph, should be selected by Shura - elected by Muslims or their representatives....