Bag can be worn like a Backpack, like a Matchbag, with a shoulderstrap or in the hand. 
Open bag (front):
The fixing for the shoulder strap can be seen, also a fixing for some pencils, a transparent pocket for notes etc, and the 2 main buckles.
Open bag (back):
Under the transparent pocket, the is a smaller compartment for a mobile phone (...) and a larger one (plastic coated inside) for a bottle. The 4 fixings on the backside allow to wear the bag (when rotated 90°, zippers mark topside) as a backpack (with the two shoulder straps unconnected) or like a matchbag (shoulder straps must be linked, Hooks can be covered with the shoulder pads), as seen on:
"Matchbag style" and "Backpack style" 
The "90°Bag system" shows the closed bag, the 2 shoulder straps and the shoulder pads to cover the hooks when bag is worn in matchbag style.