These power the ceramic heating element, as well as provide the soldering iron handle access to the thermocouple that’s placed near the actual tip. With a simple diagram [Clive] explains how ...

Most of us are used to temperature controlled ceramic heating elements ... presumably broken, soldering irons and some pieces of copper and iron along with a thermocouple for temperature ...

Despite being affordable, the Q-Ming soldering iron is rated at 80W of power, which is respectable. It has a ceramic heating element that can achieve temperatures of 356 to 896°F (180 to 480°C).