Rulesets: Groups, Factions, and Hardcore
Agree on a faction, ruleset and preferred online language, and understand PvP character limits and Hardcore progression.
Choose Normal, PvP or Roleplaying instead of a traditional realm. Hardcore will be available after launch.
Grouping requires the same ruleset and faction. Battlegrounds may match players from different rulesets, except Hardcore. These rules do not announce cross-region grouping.
Under Esc → Options → System → Languages and Social, Preferred Online Language helps you encounter players who share your preference. It applies to every character on the account and has a 24-hour cooldown between changes.
Characters cannot freely switch rulesets; create another character to try one. Dead Hardcore characters may transfer elsewhere, including PvP. Hardcore progress can carry out; outside progress cannot carry in.
PvP limits character creation to one faction and may temporarily restrict the larger faction to support balance. Normal, Roleplaying and Hardcore allow characters on both factions.
Source: Choose Your Ruleset in World of Warcraft: Forever
A fan-site summary. Dates and test content may change; consult the original announcements.