"Muslim is more a general term. All those who have just witnessed the 'Shahada' and accepts the Islamic beliefs are Muslims. Even one is weak in Islam he is still a Muslim. Mu'min is more specific, he is a Muslim with many good qualities that Allah has mentioned in the Holy Quran. He is not only praying but pray with Khushoo, He is humble, He is fearing Allah in all his actions, he preserves patience and tolerance. All the helps of Allah mentioned in the Holy Quran are behind these qualities only. Qualities of a Mu'min are listed several places. You can find them in the beginning verses of Sura Muminoon, Sura Tauba verse 112 and Sura Ahzab, verse 35 etc. Muttaqin are those having Taqwa or pious. A Mu'min is always in a situation in the heart where he always have fear and hope of Allah swt. Sincerety of heart. This is a condition of heart and only Allah can know one has Taqwa or not. Though his actions can reveal us. This is the fruit or very essence of all that makes one escape the hell fire and enter Paradise." - Ismail Eliat from Yahoo Answer. I remember another piece conversation i had with my friend about this. About the three M. I wonder which one am I? I may still be a muslim but Insya Allah i will try my best to reach being a Mu'min but the highest rank of all is being a muttaqin. So something to ponder upon... Are you a muslim? Mu'min? Or muttaqin? - عقيله