The Alliance is one of the two major political factions of the mortal races in Azeroth, its counterpart being the Horde. It consists of Dwarves, Gnomes, Humans, Night Elves (and soon Draenei). The major cities of the Alliance are: Darnassus, Ironforge, Stormwind and also The Exodar, the ship the Draenei crash-landed onto Azeroth with. The language the races communicate on is Common.
Here is a list of Alliance members and related articles on WoWRP.