Battlegroup

A Battlegroup is a group of realms whose players can face each other in arena matches. Previously, battlegrounds and Dungeon Finder instances could only bring in players from the same battlegroup, but Blizzard has removed this restriction in US realms and is in the process of removing it elsewhere.

Even once Battlegroups are eliminated, players will still be bound by their region (e.g. US players cannot group with or play against EU players) and language on the EU realms. However, language only applies within a team; for example, a French-speaking Alliance team may face a German-speaking Horde team.