An imam can be any prayer leader, or an infallible guide chosen by God
In a Sunni mosque the imam may be a salaried official or simply a knowledgeable worshipper who steps forward to lead the prayer. For Twelver Shia Muslims, the Imams are twelve infallible leaders from the Prophet's family, appointed by God. One Arabic word, meaning leader, covers both roles, a distinction outsiders frequently miss.
In Sunni practice the title is mostly functional. Whenever two or more Muslims pray together, one leads and the others follow his movements, whether in a mosque or elsewhere. Every mosque has someone in that role, though it may be a member of the congregation rather than an appointed employee, and Friday sermons are usually given by an appointed imam. According to several hadith, the choice should rest on knowledge of the Qur'an and Sunnah and on moral character. Women may lead prayers only when no men are present. No hereditary or divine appointment is needed, so in principle anyone who studies the basics can become an imam.
The word also serves as an honorary title for towering scholars: jurists, the founders of the four Sunni schools of law, experts in Qur'anic commentary such as Al-Tabari and Ibn Kathir, and pioneers of hadith science. In Turkey the job is a state post regulated by the Presidency of Religious Affairs, open only to men with a theology degree or a diploma from an İmam Hatip school, while women serve the same body as preachers and Qur'an tutors.
Shia theology gives the term far greater weight. Twelver and Ismaili Shia hold that God chooses the Imams as perfect models for humanity and keeps them free of sin, a quality called ismah. Twelvers count Fourteen Infallibles, twelve of them Imams; Muhammad's daughter Fatimah is counted infallible but is not an Imam, and the twelfth Imam, the Mahdi, is expected to emerge on the Day of Resurrection.
Imams have also ruled states. Among Oman's Ibadis the office was sometimes elective and sometimes hereditary, as under the Yaruba dynasty from 1624 to 1742. In West Africa, the Fulani Imamate of Futa Jallon alternated power between two hereditary lines from 1727 to 1896. In Yemen, a Zaidi line founded in 897 governed as priest-rulers for over a thousand years, ending with the Mutawakkilite Kingdom in 1970.
Source: Imam
