With some religions, we cannot identify a beginning date or place of origin. Judaism and Hinduism are such religions. With Islam, however, we can say when and where it began. Islam began outside Mecca, in what is now Saudi Arabia, in the year 610 AD, when the Prophet Muhammad (according to Muslim belief) got his first revelation from God.
Islam is a monotheistic religion that follows in the tradition of Judaism and Christianity. These religions have some scriptures in common and revere many of the same figures. Muslims believe that the angel Gabriel began to appear to Muhammad in a cave outside Mecca in 610 to tell him how Judaism and Christianity had gone astray and to reveal to him the Koran, which would be the most holy scripture of Islam. This is the beginning of Islam.
Islam did not become powerful or have many adherents right away. The rise of Islamic power is dated from about 630, when the Muslims, who had been in Medina, conquered Mecca. This began the rise of Muslim power, but Islam had existed since its origin outside of Mecca in 610 AD.