What is the difference between a Muslim and a Mu'min, what are the ranks of the Mu'minin, and what is the fate of a mere Muslim in the reckoning on the Day of Judgment?

Religion has three levels: Islam, then Iman (faith), then Ihsan (excellence), as indicated by the Hadith (definition) of Gabriel. The majority of Sunni scholars believe that the believer (mu'min) is of a higher degree than the Muslim, and the excellent one (muhsin) is higher than both. This is similar to Allah's saying: ﴿Then We caused to inherit the Book those We chose of Our servants; and among them is he who wrongs himself, and among them is he who is moderate, and among them is he who is foremost in good deeds by permission of Allah.﴾ [Fatir: 32]. The one who wrongs himself is the one who persists in sin, or one who has outwardly embraced Islam but has not fulfilled what is required of him in matters of faith, and he is exposed to the threat (of punishment). The moderate one is he who performs the obligatory duties and avoids the forbidden things, and this is the level of Iman. The foremost in good deeds is he who performs the obligatory duties and the supererogatory acts, and this is the level of Ihsan. Both the moderate one and the foremost (in good deeds) will enter Paradise without punishment. As for the one from whom the absolute name of Iman has been removed, and he remains at the level of Islam due to his neglect of some obligations or his committing some forbidden acts, he is subject to punishment and is under Allah's will, except that his ultimate destination is Paradise because he is a monotheist.