@Brad Humphrey

It is WiFi streaming however its not from your phone. The source is not tied to your phone, the phone is just the controller. The Chromecast does all the streaming so it doesn't eat up your phone battery. You can stream from your local content on the phone to the Chromecast but all other streaming apps such as Spotify are handled directly from the Chromecast. Any app that supports Chromecast is handled by the Chromecast.