I would like to begin this with a few defintions to help my understand the Muslim religion. Islam is defined as:
Islam
1 : the religious faith of Muslims including belief in Allah as the sole deity and in Muhammad as his prophet
2 a : the civilization erected upon Islamic faith b : the group of modern nations in which Islam is the dominant religion
Origin: Arabic islām submission (to the will of God)
First use: 1817
(Merriam Dictionary* need the other info here*)
Sun·ni
1 : the Muslims of the branch of Islam that adheres to the orthodox tradition and acknowledges the first four caliphs as rightful successors of Muhammad — compare shia
2 : a Sunni Muslim
Origin: Arabic sunnī, from sunna
First use: 1595
(Merriam Dictionary******need info********)
Shia
1 : the Muslims of the branch of Islam comprising sects believing in Ali and the Imams as the only rightful successors of Muhammad and in the concealment and messianic return of the last recognized Imam — compare sunni
2 : shiite
3 : the branch of Islam formed by the Shia
Origin: Arabic shīʽa followers, faction, sect
First use: 1626
(Merriam Dictionary********info************) There it is Islam is a religion and muslims are its followers. Much like Christianity and the christians that follow it. Muslims read the Quran as christians read the bible. Muslims believe in a higher power Ala and christians believe in God. Like Christianity Islam has many different sects two of them being the Sunni and the Shi'ia. These sects read from the same book but follow/worship in very different ways.

“The basis of Islam, and the heart of Muslim belief and thought, lie in its holy scripture, the Qur’ān, considered by Muslims to be the direct and true word of God, transmitted by the angel Gabriel to Muhammad (in Arabic) while the latter was in a state of divine inspiration akin to trance.”
(http://www.encyclopedia.com/topic/Islam.aspx)

The Sunni Muslims are traditional and believe that after Muhammed's (God) death they elected Abu Bakr father to Muhamed's wife, A'ishah, and was elected by the people of Medina to lead the Muslims in the tradions and beliefs that Muhammed had set forth. Shi'ia thought that when Muhammed past away they should follow Ali who was Muhammed's cousin and son in law married to Muhamed's daughter Fatima. Sunni's are your traditional non violent muslims while Shi'ia's are your people of Ali. These two sects could be compared to the Catholics and Prodestants. Politics is what seperates these two