A programmable thermostat lets you create a schedule that will increase or decrease the temperature in your home at set times.
A smart thermostat will also let you create a schedule, but it will also let you control it remotely from your phone. Some smart thermostats can also sense your presence in your home — or even a particular room — and then adjust the temperature accordingly. Last, smart thermostats will also connect with other smart home devices so that they can work in concert with each other.
Next: 4 ways a smart thermostat can lower your energy bill.