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 appointed his son-in-law and cousin Ali ibn Abi Talib to succeed him.Unlike the first three caliphs, Ali was from the same clan as Muhammad, Banu Hashim, and Shia Muslims consider him legitimate, inter alia, by favour of his blood ties to Muhammad, too.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.

The Quran, together with hadith (especially those collected in Kutub al-Sittah) and binding juristic consensus form the basis of all traditional jurisprudence within Sunni Islam. Sharia rulings are derived from these basic sources, in conjunction with analogical reasoning, consideration of public welfare and juristic discretion, using the principles of jurisprudence developed by the traditional legal schools.

In matters of creed, the Sunni tradition upholds the six pillars of iman (faith) and comprises the Ash'ari and Maturidi schools of rationalistic theology as well as the textualist school known as traditionalist theology.

Sunni, also commonly referred to as Sunniism, is a term derived from sunnah meaning "habit", "usual practice","custom", "tradition". The Muslim use of this term refers to the sayings and living habits of the prophet Muhammad. In Arabic, this branch of Islam is referred to as ahl as-sunnah wa l-jamāʻah , "the people of the sunnah and the community", which is commonly shortened to ahl as-sunnah.