Islam began with a man named Muhammad. The setting was in the Arabian Peninsula. Muhammad was born in Mecca in 570 A.D. At the age of 40 (610), he began having a series of visions that occurred over the next 22 years until he died in 632 A.D.
Muhammad belonged to an idolatrous tribe in which a few men were monotheists. They claimed they were neither Jews nor Christians; they traced their roots back to Abraham through Ishmael.
After three years of keeping these "visions" private, Muhammad began to "recite" what he heard in them. The content of these "recitations" was based on calling the people from their idolatry to the One True God. In doing so, he outlined many religious duties and practices that were later to become part of Islam.
Muhammad also preached on many ethical themes, such as: caring for widows and orphans, caring for the poor, being honest in business, not killing one's baby daughters the day they were born, rules for divorce and rules for sexual purity and marriage (his teaching limited the number of wives to four - an improvement over the existing practice of the Arabs at that time.)
After six years of such preaching (from 613-619), opposition from the rich began to grow as the wealthy mercantile class of Mecca controlled the idolatrous shrine trade and their livelihood was being threatened by Muhammad's preaching.
By 622, Muhammad's life was in danger. In the summer of that year, he emigrated to Medina at the invitation of the Arab tribes there.
Islam officially began in 622 when Muhammad assumed political power in addition to his claim to prophethood. The growing community of those who believed in him were called "Muslims." The word "Muslim" means someone who has "submitted." In its context, it means someone who has submitted to Muhammad and his version of God.
In the ten years between 622 and his death in 632, Muhammad bequeathed to his followers a body of administrative, political, and religious teaching that was posthumously collected into a book called the Quran. The word "Quran" means recitation.
Outside of the Quran, a body of oral tradition began to grow which was called the Sunnah, the "Trodden Path," or "Living Tradition." In due time, this "living tradition" was written down and incorporated into several volumes called the Hadith. These volumes contained a little more than 7,000 sayings of Muhammad. The Quran, by the way, is about two thirds the size of the New Testament and is divided into 114 chapters.
(Taken from Now You Can Know What Muslims Believe: A Muslim World Overview by Don McCurry. Used by permission.)