Although the Prophet Muhammad (s) was the last of all prophets, it would have been unjust if Allah completely cut off humankind from divine contact. Like Prophets, Imams act as mediums between God and humankind. After the Prophet's (s) death, the Imams of the Ahl al-Bayt (as) took on the role of guiding people and protecting the authentic interpretation of Islam.

The first two and a half centuries of Islam were the formative periods of Islam. Most of Islam’s theological and legal schools were established during this era. Most Muslims were beset by disagreements and differences of opinion during that time. The Imāms of the Ahl al-Bayt (as) however, were present during this time and made sure to establish a school that was in accordance with the pure teachings of Muhammadan Islam.

Imāmah is the greatest distinguishing factor between the two major expressions of Islam, Shia and Sunni. The Sunni belief in imāmah is a belief in fallible and completely human centered leadership. Imams for Sunni Islam can be Friday Prayer leaders, or leaders of law (like the four Imāms of Sunni law). According to Shiʿism, Imāmah is divine leadership, that is, a guided leadership by God to protect Islam and lead people to salvation.