It is in fact impossible to explain the Islamic religion in a way most Westerners would understand. The Arabic word for religion is din, which is better translated as ‘submission to law and order’, as opposed to gahl (undisciplined). Din refers not only to the individual’s belief, but also to a way of living in a very specific manner, according to strict rules laid out by the Koran and supplemented by traditions.
Islam is essentially a layman’s religion with no pope or other undisputed highest authority, no ordained priesthood, no hierarchy and no sacraments. The individual Muslim is allowed to form his own opinion on his religious beliefs, as long as he does not criticise the orthodox belief to any major extent, that is beyond the hudud (the sacred limits). Although there are many theological differences (for example between Sunnis and Shiites) there are several fundamental beliefs which every Muslim accepts.
The Muslim belief is a collection of various fragments of expression, made by Muhammed or found in the Koran. In the narrowest sense, the Muslim central belief would be the shahada, the confession of ‘Allah’s’ unity and Muhammed’s Prophethood, which is the first pillar of faith in Islam. An unbeliever can convert to Islam by reciting this simple phrase in the presence of two Muslims: “I confess that there is no god but ‘Allah’ and Muhammed is the messenger of Allah” (‘la ilaha illa allah; Muhammedon rasul Allah). However, to remain a Muslim he also has to accept the other four pillars of Sunni Islam, and combined they are known as ibadah or ‘holy serfdom’.
The ibadah was first required by Muhammed during his exile in Medina. The Muslim community (umma) had grown to become a large body of believers, which also included hypocrites, who had embraced Islam for political or economic reasons. Muhammed, and later his most pious followers, used the ibadah to separate the faithful from the hypocrites and purify the community. It consists of the five ‘pillars’ of Islam: the shahada, ritual prayers (salat), payments of the poor-tax (zakat), fasting the entire month of Ramadan between sunrise and sunset each day (sayam) and pilgrimage to Mecca once in a lifetime (hajj), if one can afford it. In addition to those five, many Muslim scholars have added the compulsion to wage a jihad. Yet these five (six) pillars are only the basic obligations of every Muslim.
 Bravmann, The Spiritual Background, 34-36.