Ahlul-kitab (People of the Book) are known as those that are of the faiths which have a revealed book/scripture. In the Qur'an, the people of the book are the Jews, Sabians and Christians.
People of the Book (Arabic: أهل الكتاب ′Ahl al-Kitāb) is a term used to designate adherents to faiths which follow the previous scriptures (meaning the Torah and the Injeel), in Arabic, Ahl-Al-Kitab (Arabic: الكتاب "the people of the Book" or "people of the Scripture"). The three types of adherents to faiths that the Qur'an mentions as people of the book are the Jews, Sabians and Christians.
In Islam, the Muslim scripture, the Qur'an, is taken to represent the completion, protector, and preserver of the truth in these scriptures, which will exist until the end of time.
