SHIA and SUNNI challenge

Islam world is divided to Shia and Sunni sect. Almost 90% of the world Muslim population has Sunni faith. Foreigners usually ask me what is the difference between Shia and Sunni religion? According to my understanding I try to give a brief explanation.

Islam is a monotheistic religion and Muslims believe their holly book Quran is an eternal reference for guiding human to truth and salvation. Mohammad as the messenger of G-d _and not the author of Quran_ was the only "human" who could perfectly understand and perform Quranic laws.

In Sunni faith there are four guides (Imam) after Mohammad who ruled Islamic society. Shia Muslims believe the guides were 12 innocents who were only the sons of Mohammad and the last Imam called Mahdi will emerge someday to rule the world into justice and piece.

The major argument between two sects is where Sunnis say after Mohammad there is no man who perceives Quran so they follow the tradition of Mohammad in his life time and also notify their four Imams as the 1st rulers of Islamic society/Ommat. That is the reason for Sunni countries to observe many of their Islamic rituals in the exact way of Mohammad time. Eventhough they may seem primitive or rigid to modern people.

Shia Muslims believe Mohammad and his 12 sons had the G-d given wisdom to perceive Quranic laws and they can guide the followers but during the time Shia people are not having an Imam in present they have to get guidance for their religious life from a religious scholar who would be chosen between numbers of major Shia scholars (Ayatollah). Therefore in Shia faith there is not necessary to follow the exact tradition of Islam in Mohammad time and some changes would happen according to the time the scholars are living in. This has been the reason why Sunni Muslims blame Shia followers for being deviated from the pure traditional shape of Islam and some of them believe "Kill a Shia and get to heaven!"