Islam is the name of the religion based on surrender and obedience to the almighty God (Allah in Arabic). A follower of this religion is called a Muslim. Hence, a Muslim is a person who surrenders his own self to the will of Allah.
According to Islam, Prophet Adam (peace be upon him) was the first man on earth and his wife Eve was the first woman. All human beings are offsprings from them. Allah revealed divine instructions to Prophet Adam (peace be upon him) to guide his offsprings. After his demise, his teachings gradually got lost. Allah sent another prophet to revive the laws of Allah. This process of sending prophets continued until the last Prophet Muhammad (peace be upon him) of Arabia.
It can seen from above that Islam is not a new religion. It is the same monotheistic religion that was revealed to other previous prophets like Adam, Abraham, Moses, Jesus (peace be upon them all), etc. Of course, since each prophet came for a specific time and people, their laws could have been different. Hence, the laws of Prophet Moses (peace be upon him) are different than the laws of Prophet Muhammad (peace be upon him).
Prophet Muhammad (peace be upon him) was honored to be last of the prophets and best one among them. The Final revelation came to him and this Holy book is known as the Qur'an.