Islam has a very large population and is dominant over any other religion in the Middle East. Its over-all-population in the world is about 1.3 billion. The majority of Muslims, however, live in Indonesia- the number of Muslims being near two hundred million.
Muslims worship the god Allah, which happens to be Arabic and Aramaic for God. To be "saved" by Allah, you must recite the shahadah, which states that you accept Islam as your one and only true religion.
To be accepted and regarded as a good Muslim, you must follow the Five Pillars of Islam. These state that you must accept that Allah is the only one true god and Muhammad is the prophet of God; you must pray during the daily prayers; you must give alms to the needy; and you must make a pilgrimage to Mecca at least once in a life time.
Muhammad founded the religion Islam during his lifetime and was greatly loved by all of his followers. He died in 632 AD, but not before seeing most of the Middle East accept Islam as their religion.