Shows class-colored blips on your map like in retail. "Party members" are shown with black dots in the center. Makes finding your friends a lot easier from the map.
Note: "Party members" are the members of your party group that was formed outside of the BG instance. The party group that forms inside the BG instance does not matter, so you don't need to move your friends into your own party group inside the BG.
Code snippets from BattleInfo addon