Backpacks are bags that possess two shoulder straps which allow the wearer to carry the bag on their back. Backpacks are often associated as a student's must have school accessory for carrying books, etc from class to class.
Luggage is any number of bags, cases and containers which hold a traveller's articles during transit. Types of luggage include suitcases, duffel bags, and tote bags. Today many types of luggage have wheels as an added convenience.