Taking all sects into account, Islam is the world's second largest religion (after Christianity) with more than 1.6 billion adherents worldwide. Islam is the majority religion in 49 countries, the largest being Indonesia. According to many sources, Islam is the fastest growing religion in the world.
The term Islam means "submission" (or "surrender"). The submission emphasized by Islam is submission to Allah, the god of Islam. A follower of Islam is called a "Muslim" ("one who submits"). A Muslim submits to Allah by obeying Allah's commands in the Qur'an (believed by Muslims to be the literal word of Allah), along with the teachings of Muhammad (Islam's prophet) contained in the Hadith (collections of stories about Muhammad).
Essential Islamic doctrines are outlined in the Six Articles of Faith, which include belief in Muhammad's teachings concerning (1) Allah, (2) angels and other spirit beings, (3) prophets, (4) scriptures, (5) the Day of Judgment, and (6) predestination. Core Muslim practices are listed in the Five Pillars of Islam and consist of (1) reciting the Islamic Creed, (2) performing prescribed Islamic prayers, (3) giving alms in accordance with Muhammad's teachings, (4) fasting during the Month of Ramadan, and (5) taking the pilgrimage to Mecca. http://www.answeringmuslims.com/