Who are the Horde and Alliance?
The Horde and Alliance are the two sides battling for control of the world. In years past, they fought brutal wars against each other, but today, they have settled into a tenuous stalemate. Occasional skirmishes still erupt between the two sides, but open warfare is no longer raging across the continents. Still, the Horde and Alliance are hostile to each other, and members of one faction are never welcome in the cities of the other.

The ten races you can play are split equally between these two sides.

Alliance: Draenei, Humans, Dwarves, Night Elves, Gnomes
Horde: Blood Elves, Orcs, Tauren, Trolls, Undead

Can I switch my character's faction from Horde to Alliance or vice versa?
No. You can create both Horde and Alliance Characters. On PvP servers, you can only create characters on one side for that server.

Can I have both a Horde and Alliance character on the same Realm on a single account?
On normal servers this is possible, but on player-vs.-player servers it is not.

Can players trade with members of the opposite faction?
No. In general, you cannot trade with players of the opposing faction. However, you can place items up for auction at the neutral auction houses at Everlook, Gadgetzan, and Booty Bay. Players from either faction can bid on these items, meaning you can buy and sell with opposing players at this neutral auction house.

Can I group or communicate with members of the opposite faction?
You cannot form groups with members of the opposite faction, nor can you understand their language - making interpersonal communication with the other faction difficult. Default emotes such as /laugh, /nod, /salute, and /taunt will be your only means of direct communication.

Well, can I fight the opposite faction?
Yes! Faction vs. faction combat is encouraged, particularly on PvP servers. You will have opportunities to fight the other faction in Battlegrounds, world PvP, Arenas, and even duels. On Normal servers, world PvP is consensual - players have to toggle their /pvp flag or attack a flagged target to participate.