All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
1. The Quran is the Words of Allah sent down to Prophet Muhammad via Gibreel in Arabic Language.
2. A Muslim is one who is characterized by Islam. Islam means obedience, submission and peace. It is to commit one's self totally to Allah, making one's will subservient to and in complete harmony with the Will of Allah, as well as denial of Shirk. Its pillars are: The Two Testimonies of Faith, Prayer, Zakat, Fasting and Hajj.
3. A Mu’min (believer) is one who is characterized by Iman (faith). Iman is the belief of the heart and confession of the tongue to the truth of Islam and the performance of the pillars of Islam.
It increases with good deeds and decreases with evil deeds. Iman without action is of no use, nor is action without belief of any value.
The Pillars of Iman are: belief in Allah, His Angels, His Books, His Prophets, the Last Day and Predestination; be it good or bad. Iman includes the pillars of Islam and all inner actions of the heart, such as fearing Allah Alone, loving Him, being humble to Him etc.
By and large, one who believes in the principles of Islam, the pillars of Iman (in word and deed), and avoids what is forbidden becomes a true Muslim and a faithful Mu’min.
For more benefit, please refer to Fataawa 83219 and 84243.
Allah knows best.