It uses battletags of those with the addon to provide an interface for both creating and joining premade teams. Used mostly for rated bg's but can be used for anything else as well.
It facilitates xrealm group organisation as well and after installing it over the weekend I've found it much easier to cap a couple of char's.
Easy to use and should get faster and faster to find teams the more people use it.
Particulary useful if you find yourself without the rating to get in higher rated guild teams yet and/or end up spamming trade chat for groups/pugs. Many games run without comms even as well.