How do power fan thermostats actually work?

The thermostat is a device used to set a temperature to tell the power fan when to come on when the temperature in the area exceeds the set point.

The thermostat is a device used to set a temperature to tell the fan when to come on when the temperature in the area exceeds the set point. So when the temperature in the area, room, attic is above the set point it will bring the unit on and when the temperature is below the set point it will turn the unit off.