The Plex Media Server is a backend application to help you manage and stream media to almost any network connected device.
This app has been integrated to ClearOS's Network Map app that allows you to restrict when users/devices on the LAN can access the media server - a useful feature if you allow guests on your network but do not want them to automatically have access to your family photos, music etc.
Smart phones, iphones, Windows and Mac desktops have dedicated client applications to stream or display media from your server. Linux desktops can stream the media via an HTML5 browser.
Most game consoles like the PS3 are also able to automatically find the service and be used to playback via your television.
To learn more about this app, click here
Documentation for ClearOS 6 can be found here.
Documentation for ClearOS 7 can be found here.