The two main branches of Islam are Sunni and Shia Islam. The primary difference in their beliefs is the succession to Mohammad. Another difference is the interpretation of the Koran.
Sunni Islams believe that Mohammad intended for the Muslim community to choose a successor by consensus. The name "Sunni" means "traditional," and the followers believe the Koran is authentic and may not be added to or taken from. Approximately 90 percent of Muslims are Sunni.
Shia Islams, or Shiites, believe that Mohammad chose his son-in-law, Ali, to be his successor. Their name means "partisans" and they reside primarily in Iraq, Iran and Yemen. They view the Koran as unauthentic and offer their own interpretations to its doctrines.