Describe the motion of charges from one terminal of a battery to the other through a flashlight.

The DC current leaves one terminal, travels through the switch and goes into the bulb. There it drops its voltage across the bulb and releases the electric potential energy in the form of light and heat. (in conventional bulbs most of this energy is heat which is why LEDs are more efficient). Then the charges that comprise the current are at ground potential and return to the battery.