A smart house is one that has electronic controls to regulate temperature, lights and equipment in an energy efficient manner.
Smart houses have a central computer that runs all the controls, from regulating air temperature to when the lights come on. Depending on the type, you can also call into the computer and have it do specific things such as turn on a hot tub as you drive home from work.
If built from the ground up or through extensive remodeling, a smart house may include special wiring that allows the computer to only send power to outlets when something is plugged in and in use. This wiring also allows the computer to determine what volts are needed rather than assuming the appliance needs all 110 volts typically supplied to outlets.
Smart houses are currently being built for people with dementia who live in group homes in the United Kingdom. The systems in these houses focus on ensuring stoves are turned off, that residences remember to take medicine and that the live-in caregivers are alerted should one of the residents attempt to wander during the night.
If you want to implement a smart house, there are small things you can do now to start, like installing a programmable thermostat or motion sensor light switches.