In Islam, there are two major schools of thought, the Shi'a and the Sunni which have more in common than differences.
They follow the same book-The Qur'an; the same prophet Muhammed, offer their prayers 5 times a day, fast in the month of Ramadan and go for Hajj-pilgrimage to Mecca. Those who follow Prophet Muhammed, in accordance with his sayings and actions, are called Sunni?and those who in addition also follow the sayings and views of Ali(Muhammed's son-in-law), whom they consider as the rightful successor to Prophet Muhammed, are called Shi'a.
The word Shi'a means a partisan (party of Ali and it started more as a political party to help Aliin his conflict with his political adversaries. Most Shi'a? live in Iran, Iraq and Azerbaijan while the rest of the Muslim world is mostly Sunni - Shi'a comprise about 16 percent of the Muslim population.