Thermostat Setback refers to moving the thermostat warmer during cooling/Air Conditioning weather and setting the temperature cooler on the thermostat during heating season.
At a 70 degree delta T (temperature differential) you will save an estimated 1% on your energy costs over an 8 hour period. That means if while you're gone to work in the winter, if you reduce the temperature of your home for 8 hours, by 10 degrees, you will save roughly 10%.
Although it will take some extra energy to reheat the home back to comfortable settings - it will never be as much as the energy saved, and most of the time it makes sense to use temperature setbacks.
The only time you wouldn't want to use setbacks is with an electric heat pump, a super insulated home, or if there is a radiant slab with a large thermal mass that is being heated.
Here's our buddy Richard Trethewey explaining how it works:
Our Lux GEO Thermostats (currently buy 3 | get 1 free) have WiFi capabilities to easily monitor and setback the temperature. They are fully programmable, can be controlled with Amazon Alexa or Google Home, have Geofencing capabilities allowing the home to go into automatic setback when the last person is outside of their pre-set geofence, and can work with indoor air quality sensors to improve overall indoor air quality.