The first tool is the addition of clans, Diablo III's version of guilds. Anyone can form a clan, although a player may be part of only one clan at a time. Clans are limited to 120 members and will be searchable with a clan finder feature.
Then there will be communities, which are larger and more casual social circles within the game for like-minded players. Unlike clans, communities can support unlimited members, and players can be part of more than one at a time. Communities and clans will be supported by a new interface in the game that includes messages of the day and achievement notices.