The red arrows represent the path of the electricity.

The electricity travels from the power cord to the switch where they both connect. When the switched is turned on the power goes from the switch to 2 places.

The 1st place it goes is to a giant resistor under the metal pipe that transports the water. This resistor is the pot heater and water heater.

The 2nd place the power goes is to a temperature regulator, which makes sure the temperature of the water and the pot don't go above a certain point.