A programmable thermostat is a device that automatically adjusts the temperature in your home based on a pre-set schedule. This allows you to set different temperatures for different times of the day, helping to save energy and reduce heating or cooling costs. These thermostats can be programmed to lower the temperature when you're away or asleep and raise it before you return home. Many modern programmable thermostats also offer features like Wi-Fi connectivity, allowing you to control your home's temperature remotely using a smartphone or tablet.