Even though the differences may not seem obvious the fans and fanboys/fangirls of the world are quite different from each other, starting with the fact that anyone can be a fan but only the truly obsessed become fanboys.
This obsession twists the poor little fanboys and fangirls into creatures fueled by pop culture, who live to argue about their favorite franchises while waiting for the next release.
Many diehard fans will refer to themselves as fanboys, but as this comic by Tom Preston shows you're only really allowed to add the "boy" or "girl" to fan when you've taken all the joy out of being a fan!
-Via Geeks Are Sexy