We start by the name of God, Allah, the Creator of All things, the only one who deserves to be worshipped, the merciful to the believers and non-believers in this world, and the one whose mercy is only for the Believers in the hereafter, the one who is attributed with attributes of perfection and is clear of any imperfection and the one who does not need any of his creations. We ask Allah to guide the misguided ones to the correct path and the true religion.

What is Islam?
Linguistically, Islam means submission, a specified submission. It is the submission to what the prophet brought. This takes place by uttering a statement called ‘shahadatayn’ – the two testifications of faith. Belief, on the other hand, linguistically means a specified certitude. It is to accept as true what the prophets brought. Islam is not acceptable without Belief and Belief is not accepted without Islam.
The least of Belief is belief in the two testifications of faith, the belief in the oneness of God, Allah, and in the belief in the Prophets that God sent.

It’s important to know that Islam, the submission to one Creator, the belief that there’s only ONE God that deserves to be worshiped, is the Religion of all the prophets. There is only one true Religion–that of believing the correct belief in Allah and His messengers, worshipping Allah only, loving, respecting, and following the prophet of the time, and loving and respecting other prophets. Every prophet and messenger followed and called people to the same Religion; this Religion is called ISLAM.

A believer in Islam is called a MUSLIM. And to make it clear, the meaning of Islam is “to submit to Allah”. The meaning of the word Muslim is “one who submits to Allah.” The name Allah is the name of the only true God. Although prophets and messengers spoke different languages, what they called people to was the same Religion. A person can declare that he believes and follows the true Religion–Islam–in any language, for belief is known to Allah regardless of the language. Those who say they are Muslim, yet deny the true belief in their heart, with their tongue, or by some actions, are surely not Muslim. Allah knows fully who are the ones who truly believe in Islam. Both messengers Moses and Jesus called their people to the true Religion–Islam–which is clearly described in the Quraan–the last and preserved scripture for all of mankind on earth.

This was a short intro about the meaning of Islam and Muslims.

See related topics regarding this topic under this link:

http://alsunna.org/Islamic-Beliefs