Not really, it actually comes from being chosen by the staff that see how well a person is active and follows the rules very well, helps out other users regardless of who they are and never asks/demands to become one.
So even a normal user can end up being chosen by the staff members.
Hm... ranks... well we've got the supporters with the tiers 1 through to 6 that can be achieved by donating to PC, we've got the moderators keeping the threads in their forum neat and tidy, then we've got the super moderators that keep a watch over every single forum and making sure they're neat and tidy, then we've got the assistant admins that help out with inserting the HTML codes and stuff like that, and finally we've got the staff admins and the site admins that can pretty much do anything on the forums. And there ya go, there's the ranks! More information can be found here.