One and a half billion people from a vast range of races, nationalities and cultures across the globe - from the southern Philippines to Nigeria - are united by their common Islamic faith. About 15% live in the Arab world; the world's largest Muslim community is in Indonesia; substantial parts of Asia and most of Africa are Muslim, while significant minorities are to be found in the Soviet Union, China, North and South America, and Europe.
The followers of Islam are called Muslims. Muslims are not to be confused with Arabs. Muslims may be Arabs, Turks, Persians, Indians, Pakistanis, Malaysians, Indonesians, Europeans, Africans, Americans, Chinese, or other nationalities.
An Arab could be a Muslim, a Christian, a Jew or an atheist. Any person who adopts the Arabic language is called an Arab. Muslims all over the world try to learn Arabic so that they may be able to read the Qur'an (the Muslim holy book) and understand its meaning. Although the Qur'an has been translated into most languages, to truly appreciate its depth it is beneficial to read it in Arabic.
Source Islamic Dictionary