Smart thermostats are Wi-Fi thermostats that can be used with home automation and are responsible for controlling a home's heating, ventilation, and air conditioning. They perform similar functions as a Programmable thermostat as they allow the user to control the temperature of their home throughout the day using a schedule, but also contain additional features, such as sensors and Wi-Fi connectivity, that improve upon the issues with programming.
A Nest Labs thermostat
Honeywell Manual Thermostat
The Nest Web Portal allows users to remotely change the temperature, create a schedule, and view past energy usage.
The Ecobee 4 thermostat
A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint.
Honeywell's "The Round" model T87 thermostat, one of which is in the collection of the Smithsonian.
Next Generation Lux Products TX9600TS Universal 7-Day Programmable Touch Screen Thermostat.
A Honeywell electronic thermostat in a retail store
Car engine thermostat