Who is a Muslim? Well, a Muslim is someone who follows the religion of Islam. By following Islam he submits his will to Allah.
Muslim is he who declares that there is none worthy to worship except Allah and Muhammad is his messenger. Just by declaring this he is now Muslim and Allah will judge him according to his heart whether he believes in it or not. I am saying this cause nowadays we have become the judge.
In Quran Allah tells us that all the prophets were Muslims.
Why do Muslims tell people to accept Islam?
We all know that Allah sent prophets from time to time to guide people to his religion. But after sending his final messenger Muhammad Allah gave Muslims the job of dawah (Inviting people to Islam). So now first we have to become people who do good on this earth. Then we have to invite people to Islam. But we can not do that for worldly gain. If we do Allah will make people accept Islam through us but we will not get anything in the hereafter.
Who is a Muslim now you tell me who is Jew, who is Christian and who is Hindu? If we Think carefully with our mind free from everything.We will understand that a person who follows his religion in the correct way then he is of that religion. So we must not think of those who do wrong in the name of a religion because they are not of that religion.