A thermostat is a device that is used to regulate the temperature of a room, house, or other space. It measures the temperature of the air and uses a thermostat setting to turn the heating or cooling system on or off as needed. This helps to maintain a comfortable temperature and helps to conserve energy by not running the system unnecessarily. Some thermostats also have options for programmable settings and can be set to turn the heating or cooling system on or off at specific times, such as in the morning or when leaving for work.