FAQ 8.1 - What's a clan?
Clans are groups of players that band together either for friendship, gain, grouping, or other reasons. Clans generally last longer than a single group, with most clans being around for months or even years. You don't need to be in a clan at any level, but a lot of players enjoy it. After you gain a few levels and are comfortable with the game, ask other players about clans and which clans are accepting new members.