Islam  is a monotheistic, Abrahamic religion originating with the teachings of the Islamic prophet Muhammad, a 7th century religious and political figure. The word Islam means "submission", or the total surrender of oneself to God. An adherent of Islam is known as a Muslim, meaning "one who submits [to God]". 
There are between 1 billion and 1.8 billion Muslims, making Islam the second-largest religion in the world, after Christianity.

Muslims believe that God revealed the Qur'an to Muhammad, God's final prophet, through the angel Gabriel, and regard the Qur'an and the Sunnah (words and deeds of Muhammad) as the fundamental sources of Islam.

 They do not regard Muhammad as the founder of a new religion, but as the restorer of the original monotheistic faith of Abraham, Moses, Jesus, and other prophets. Islamic tradition holds that Jews and  distorted the revelations God gave to these prophets by either altering the text, introducing a false interpretation, or both. Source: See Wikipedia.org