That means wheneveryoumakea voice call while the phone is connected to a Wi-Fi network, your Republic phone places it over Wi-Fi rather than using a costlier cellular phone network.
Sprint TV's also included, of course, but it just hangs on 4G wheneveryou try to watch a program -- we had to turn it off and use EV-DO to make it work, which is pretty counterproductive considering how much better it could look on a faster, lower-latency connection.