Mechanical Elements:
Power Switch: The above image is a circuit diagram for the screwdriver. This works by causing the current to switch directions depending on which way the switch is flipped. On one side, the switch is connected to the positive side of the motor, and when the switch is flipped to the other side it is connected to the negative side of the motor. This allows the screwdriver to turn both clockwise, and counterclockwise.
Locking Mechanism: The locking mechanism holds the drill in one of the above three positions. It does so by having two sets of interlocking teeth within the drill that lock the position. The lock button is held out by a spring that keeps these teeth sets together. When the button is pressed, the teeth no longer interlock, allowing you to switch between positions. This gives the screwdriver a couple of orientations for different types of use.
Power / Manual: On the tip of the drill, there is an option to switch between power and manual. When this is set to manual, the gear box locks, so nothing can turn inside. This protects the gears from accidentally activating or turning at all. This protects the screwdriver from gears getting stripped and ruining the gear box.