Islam has about 1.5 billion believers spread around the world. The faith believes in the same monotheistic God as the Old and New Testaments, but that the final messenger of God was Mohamed, who in A.D. 610 began to receive new revelations from God. Those revelations were written in the Muslim holy book, the Quran. Eventually the religion broke into two main factions: Sunni and Shia.

The Split Between Shia and Sunni

The division between the two tribes of Islam dates all the way back to 632 and the death of Muhammad. There was a dispute over who should oversee the spread of the religion, since none of Muhammad's sons had lived to maturity. The Sunni division believed the rightful successor was Abu Bakr, who was selected by a group of Muhammad's followers. The Shia division believed that Ali, Muhammad's cousin and son-in-law was the rightful ruler. The majority of Muslims supported the Sunni view and would go on and expand the territory of Islam from the 600s to the defeat of the Ottoman Empire in World War I.

What Sunnis Believe

Sunnis share the basic beliefs of Islam with Shia, including the authentic teachings of the Quran and the five pillars of Islam: Shahadah (professing Muhammad as God's true messenger), Salat (the five daily prayers), Sawm (fasting), Zakat (tithing and giving alms) and Hajj (the pilgrimage to Mecca). Sunnis also believe in hadiths, which are other writings of the wisdom of Muhammed. They believe that two hadiths, the Sahih al-Bukhari and Sahih Muslim, are the most authentic. Sunnis are the more orthodox of the Muslim tribes; Sunnis disagree with Shia on the identity of the final imam.

What Shias Believe

Shia's believe in the basic tenants of Islam, including the Quran, but there are significant differences in their belief in the clergy and in the ultimate fate of the world and the religion. At the end of the world, the Shias believe that Muhammad ibn Hasan Al-Mahdi will return to Earth, along with Jesus, to rule as Islam's final imam. Shias also believe that spiritual leaders cannot be elected by men, but must be chosen instead by God. This stems from the division between Ali and the other leaders which led to the original split in the faith.

Where Sunnis and Shias Reside

Sunnis and Shia still share much territory in the Middle East, Africa and into Europe and India. Sunnis make up 80 percent of the population of Muslims in the world, including most of the Islamic holy land of Saudi Arabia, Turkey and North Africa. Shias have a majority in Iran and have pockets around the area. The countries which have significant populations of both tribes have seen conflict arise, especially in Iraq and Pakistan.