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. However, the language of the Qur'an (the Holy Book of Islam) is Arabic. Muslims all over the world try to learn Arabic so that they may be able to read the Qur'an and understand its meaning. They pray in the language of the Qur'an, namely Arabic. Supplications to God could be in any language.
While there are one billion Muslims in the world there are about 200 million Arabs. Among them, approximately ten percent are not Muslims. Thus Arab Muslims constitute only about twenty percent of the Muslim population of the world.