A Thermostate is a device that automatically regulates temperature, or that activates a device when the temperature reaches a certain point. The an automatic device for regulating temperature (as by controlling the supply of gas or electricity to a heating apparatus). It uses temperature to determine when it needs to turn the fan and AC or heat on and off. It actually works kind of like a light switch, except it incorporates temperature. The Thermostate is very useful and easy to install.