Orthodox Islam

Sunni Islam (/ˈsuːni/ or /ˈsʊni/) is the largest denomination of Islam. Its name comes from the word Sunnah, referring to the exemplary behaviour of the Islamic prophet Muhammad. The differences between Sunni and Shia Muslims arose from a disagreement over the choice of Muhammad's successor and subsequently acquired broader political significance, as well as theological and juridical dimensions.

According to Sunni traditions, Muhammad did not clearly designate a successor and the Muslim community acted according to his sunnah in electing his father-in-law Abu Bakr as the first caliph. This contrasts with the Shi'a view, which holds that Muhammad intended his son-in-law and cousin Ali ibn Abi Talib to succeed him. Unlike the first three (Rashidun) caliphs, Ali was from the same clan as Muhammad, Banu Hashim, and Shia Muslims consider him legitimate by favour of his blood ties to Muhammad. Political tensions between Sunnis and Shias continued with varying intensity throughout Islamic history and they have been exacerbated in recent times by ethnic conflicts and the rise of Wahhabism.

...
Wikipedia