Ahl al-Kitab means "People of the Book" — Jews and Christians. The Qur'an permits their food, which is why scholars discuss kosher meat.
Ahl al-Kitab (أهل الكتاب) means the People of the Book, a term for Jews and Christians. The Qur'an says "the food of those given the Scripture is lawful for you" (5:5).
Scholars differ on how this applies today — for example whether supermarket meat or kosher meat counts. See Is kosher meat halal?