Virtue: Explained in Two parts....
First part - A Muslim means a person who submits their will to God. He or She believes God is one, has no partners, no idols, no paintings, does not give birth nor was he born. God is one and the only...in Islam we call "Allah". He is the creator, inventor, maker, and manufacture of everything! There is beautiful chapter in the Quran called "Surah Ikhlas - Chapter 112" - in it Allah (God) mentions 4 lines criteria and definition of Allah (God).
Say, "He is Allah, [who is] One,
Allah, the Eternal Refuge.
He neither begets nor is born,
Nor is there to Him any equivalent." (Surah Ikhlas 112 Verse 1-4)
In Islam we try to abstain from using the word God...because it can be played-around with. For example, if you add "father" to the end of the word "God" it becomes "Godfather". There is nothing like God Dad! He is unique and there is nothing like him. He is permanent….we are temporary, one day we will have to leave this materialistic world (dunya) and return to him. "Indeed we belong to Allah, and indeed to Him we will return." Quote from Surah Al-Baqarah [Chapter 2: Verse 156]
Understand so far.....?
Second part - We have been instructed by Allah in the Quran to follow the teachings of the last and final messenger Prophet Muhammad (Peace Be Upon Him), the best creation in the whole Mankind. “O you who have believed, obey Allah and obey the Messenger.” Quote from Surah An-Nisa [Chapter 4: Verse 59] “Muhammad is not the father of [any] one of your men, but [he is] the Messenger of Allah and last of the prophets. And ever is Allah, of all things, Knowing.” Quote from Surah Al-Ahzab [Chapter 33: Verse 40]
His teachings are called the "Sunnah". These are directly given to him by Allah, and to us through his blessed lips. The Quran is the word of Allah revealed to Prophet Muhammad (Peace Be Upon Him) through Angel Gabriel (AS). This entire book has remained 100% in its original form since revelation. Everything in Islam is based on the Quran and Sunnah.
There you go, now you know what a true Muslim is...Thanks for Reading.
Reference: Surah Ikhlas 112 Verse 1-4