ADE, do you or do you not know what a clan is?
A clan is a group of members that play a certain game, usually their are different ranks based on your skill, but not always.
The benefits of being in a clan are that you all get to play together, you can communicate and get things done better, participate in clan-only events, and if you're part of a good clan, people will notice that and see that you are high up there, and not some noob who just joined.