This is known as the Sunni - Shia Divide. The Shia followers supported Muhammed's cousin and son in law, Ali ibn Abi Talib, because they believe that a blood relative should succeed Muhammed as they come from a divine blood line. The Sunni believers are proponents of Abu Bakr who was a prominent leader and companion to Muhammed, and were opposed to using bloodlines as basis for political leadership.
Reports say that the majority of Muslims are Sunnis towering 85% of its members.
