The three parts of the controlling electronics are (from left to right in the first image): the charging port, the trigger mechanism, and the direction switch.

The charging port (second image) charges the battery when a DC power supply is inserted into the connector. The port also lights up a red LED while charging.

The trigger switch controls the speed of the motor by connecting more of the batteries as the trigger is depressed further.

The direction switch controls the polarity of the voltage connected to the motor, which spins the motor either clockwise or counterclockwise.