The word "Muslim" means one who submits to the will of God. This is done by declaring that "there is no god except one God and Muhammad is the messenger of God."
In a broader sense, anyone who willingly submits to the will of God is a Muslim. Thus, all the prophets preceding the prophet Muhammad are considered Muslims. The Quran specifically mentions Abraham who lived long before Moses and Christ that, "he was not a Jew or a Christian but a Muslim," because, he had submitted to the will of God.
Thus there are Muslims who are not submitting at all to the will of God and there are Muslims who are doing their best to live an Islamic life. One cannot judge Islam by looking at those individuals who have a Muslim name but in their actions, they are not living or behaving as Muslims.
The extent of being a Muslim can be according to the degree to which one is submitting to the will of God, in his beliefs and his actions.
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Islamic guide...
Diversos"One who submits to Allah SWT" Islam means Peace through the Submission of God