Islam originated in Arabia (specifically in the cities of Mecca and Medina) during the early 7th century AD. Muhammad founded Islam after receiving (or claiming to receive) divine revelations from an angel named Gabriel which explained the words of Allah, the Muslim word for God. Muhammad later compiled these revelations into the Qur'an, the holy text of Islam.
Islam expanded rapidly during the middle ages through military conquest, enveloping most of the Middle East and much of northern Africa. Today, the epicenter of Islam remains in the Middle East. The Muslim faith has spread further south into Africa and even contains many adherents in regions of the world which are primarily Christian, such as western Europe and the United States. According to Pew Research, there were more than 1.6 billion Muslims in the world as of 2010.