Islam was established as a religion by Mohammed (570-632 CE) who is viewed, by Muslims, as a last prophet of God. His sayings are collected in the Koran (Qur'an) where they are arranged in order of length. Second-party rememberances of him are termed as Hadith. All written collections of his sayings were burned after the authoritative collection was made after his death, and only the Arabic version is considered authoritative.
The principal divisions of Islam are Sunni (commonly described as orthodox) and Shia Islam (sometimes transliterated Shi'a Islam as there is no universally accepted means of writing Arabic words with roman type). They form majorities in southern Iraq and Iran, and are one of Lebanon's several minorities. They are also minorities in Pakistan and Afghanistan (Hazzara). Because of the emnity between Sunni and Shi'tes, there is an on-going theological and violent conflict between the two.
Seen as heterodox by many other Muslims, the Ismailis are members of the branch of Shia who recognized the sixth imam, Jafar al-Sadiq's son Ismail, as his successor. They are led by his descendant, the Aga Khan. Ismaili theology recognizes the authority of Imam as the authoritative interpreter of the esoteric or hidden meanings of the faith.
The Five Pillars
The five pillars of Islam constitute the most basic tenets of the religion. They are:
Faith (iman) in the oneness of Allah and the finality of the prophethood of Muhammad (indicated by the declaration [the Shahadah] that, "There is no God but Allah and Muhammad is the messenger of Allah"), keeping of the five scheduled daily prayers (salat), almsgiving (zakat), fasting (sawm), and pilgrimage (hajj) to Mecca for those who are able.
Jihad literally translates as "struggle." Strictly speaking, jihad does not mean "holy war" as some often point out. However, the question remains as to what sort of "struggle" is meant: an inner, spiritual struggle against the passions, or an outward, physical struggle.