Most powertools have something in common : they use a rotary motion. The idea is to reuse the same motor for different tasks by changing the front part of the powertool. Therefore, you save not only the motor, but a lot of material when buying a new powertool (or accessory in this case).
I didn’t had time to draw the function of the rotating handle : by changing the shape of the object you can create other powertools such as this one :
http://www.professional-power-tool-guide.com/Pictures/Dewalt%20Cutout.jpg