Muhammad was born into the clan of a powerful Meccan family. Orphaned at the age of six, Muhammad was raised by his grandfather and uncle.
Muhammad took great interest in religion and often spent time alone in prayer and meditation. At about the age of 40, Muhammad's life was changed overnight when he believed a voice called to him while he meditated in a cave outside of Mecca. According to Muslim belief, the voice was that of the angel Gabriel.
He who told Muhammad that he was the messenger of Allah. "What shall I proclaim?" asked Muhammad, and so the voice answered;
"Proclaim! In the name of thy Lord and Cherisher, who created man out of (mere) clot of congealed blood. Proclaim! And thy Lord is most bountiful. He who taught (the use of) the pen taught man that which he knew not" - Qur'an, sura 96:1 - 5
After much soul-searching, Muhammad came to believe that the Lord who spoke to him through Gabriel were in fact Allah. Muhammad became very convinced the he was the last of the prophets. Thus, he began to teach that Allah was the one and only God and that all other gods should be abandoned.
People who agreed to this basic principle of Islam were called Muslims.
By 613, Muhammad had begun to preach publicly in Mecca, but he met with some hostility. Many Meccans believed that his revolutionary ideas would lead to neglect if the traditional Arab gods. They feared that Mecca would lose its position as a pilgrimage center if people accepted Muhammad's monotheistic beliefs.
After some of his followers had been attacked, Muhammad decided to leave Mecca in 622. Following a small band of supporters he sent ahead.
Islam Expands;
Muhammad had not named a successor or instructed his followers how to choose one. Relying on ancient tribal custom, the Muslim community elected as their leader 'Abu-bakr', he who was a loyal friend of Muhammad. In 632, Abu-bakr became the first successor.
Islam spread quickly due to its military might, strategy, and large, extremely cohesive armies. Islamic armies came in and totally pwned reigning empires. They would build giant, imposing mosques from where the 'azaan' could be heard to great distances. You would notice that people bowed down to invisible deities in great congregations, and then proceed with their daily routine of prayer, five times a day.
"Islam simply means the religion of complete submission to the will of God. Whoever submits their will completely and worships God only in the way God has commanded and walks on the path of the Prophet that was sent to their time is a Muslim."