The wires is what is needed to put together the whole thing, kinda like glue when you're gluing a piece of paper on it.
Anyways, the battery is the main source and main energy per say.
That energy that comes from the battery, thanks to the wires, it can transfer that said energy to both the switch and light bulb.
And as you flick the switch, it depends of how you put it together, there's two options, turning the light bulb on or turning it off.
Though it doesn't mean that since the light bulb is connected to the battery makes the bulb turn on no matter what since the switch can cancel the main source's energy.
- Ouma :>