A thermostat is a device used to control the temperature in a building by turning the heating and cooling equipment on and off as needed.

The thermostat will often contain a temperature sensor within it (or it is connected to a temperature sensor)

The location of the temperature sensor is important because that will control the operation of the air conditioning or heating. It may also determine the airflow and/or the supply air temperature provided to a zone.

In general, each thermostat controller represents an airside zone (even if the zone contains more than one room)