(Musarrif al Qulub). Allah is the One Who turns the heart whichever way He desires. It was narrated from Anas ibn Maalik that the Messenger of Allah (may the salutations of Allah be upon him, and peace), used to say often: “O Controller of the hearts, make my heart steadfast in adhering to Your religion.” I [Anas] said: “O Messenger of Allah, we believe in you and that which you have brought, do you still fear for us?” He said, “Yes, for people’s hearts are between two of the fingers of the Most Merciful and He turns them as He wills.” (Narrated by al-Tirmidhi (2140).
Islam means peace and the person who follows this peace is called the Muslim. From another root meaning of the word, Islam means complete submission and surrender, and the person who submits and surrenders himself to the will of his Lord is the person who has accepted Allah as his Creator, Sustainer, Lord and the Master of the Day of Judgement.
So from both the definitions Islam means a way of life for people who have opted to follow peace as opposed to chaos, order as opposed to disorder, discipline as opposed to indiscipline, submission as opposed to refusal, surrender as opposed to insolence, obedience as opposed to disobedience etc. All these things combined together to define Islam as away of life by which a person becomes a follower of peace and not a follower of chaos. And the followers of peace are the Muslims whose duty it is: "to establish peace and what is good, and to prevent chaos and what is evil, and they are the best people." (Al-Qur'an 3:110)