In general. a clan is a group of people that work together to accomplish goals. They are a little more advanced than just a trooper. because there is a limited chat feature where you can post messages and communicate. There are ongoing series of challenges such a boss you all hit, and periodic game events where clan members complete certain in-game tasks to earn rewards. The clan has it's own store of items for sale as well. When choosing a clan, you want to look for several things. 1. Is the clan taking members of my level? 2. How close to full is the clan? 3. What is the level of the clan? 4. Most importantly is how active are members of the clan? You want to take all these things into consideration when joining a clan. One that completes in-game achievements but has 3 slots open for members and is level 17 might be better to join than say, a level 20 with a lot of inactive members. One final thing is, assess how active you believe that you can be in Clancy activities such as hitting the clan boss daily, and working to complete challenges during events. Pick one that matches your level of participation for best enjoyment.