A backpack—also called knapsack, schoolbag, rucksack, rucksac, pack, sackpack, booksack, bookbag or backsack—is, in its simplest frameless form, a fabric sack carried on one's back and secured with two straps that go over the shoulders, but it can have an external frame, internal frame, and there are bodypacks. In the era of more and more individuality, various styles such as simplicity, retro, and cartoon also cater to the needs of fashion people to show their individuality from different aspects. http://www.galaxytrendbags.com/backpack/