Z order refers to instructions for the overlapping of two-dimensional objects.
In Boom Learning this means the instructions for the stacking of widgets (text, image, container, etc). Setting the Z order determine what is foreground and background relative to each other.
Draggables are always "Front". You cannot change the Z Order for a draggable.
Drop Zones can be behind a different object.
Use Back and Forward to move an object one step behind or in front of another object.
Use Rear to move an object all the way to the rear.