Approximately one-fifth of the world's population is Muslim, concentrated in an area on either side of the equator and stretching from Morocco in the west to the Philippines in the east. Islam means "submission to the will of God"; Muslims are "submitters" to God's will as it was communicated to the prophet Muhammad in a series of divine revelations. The Muslim scripture (the Qur'an) contains these revelations, and it is considered to be the eternal speech of God.Muhammad's call to prophecy occurred in about 610 CE. By the time of his death in 632 he had established the structure of a new religious outlook, and he had brought the whole of the Arabian Peninsula under his sway. Controversy over headship of the Muslim community led to a major division among the faithful. Those known as the Shi'ah Muslims advocated a hereditary succession, while Sunni Muslims (today the large majority) held to a principle of election.
In the years immediately after Muhammad's death, Islam spread quickly throughout the Middle East. This expansion laid the foundations of a mighty empire that reached the zenith of its political and cultural brilliance in the 9th and 10th centuries, under the caliphs of the Abbasid dynasty (who established their capital in Baghdad). In subsequent waves of expansion, Islam spread across North Africa and then into Europe, Central Asia, the Indian subcontinent, the Indonesian archipelago, and even farther east.
Religiously speaking, for Muslims the central human problem is our need of guidance. History is a repeated process of receiving guidance through prophecy and then of falling away from it. Muslims see Muhammad as the last of a great series of prophets that began with Adam and continued with others such as Abraham, Moses, David, and Jesus.