A fanlisting is a place for all fans of a particular show, movie, actor/actress, singer, etc. to come together and build the biggest listing of people from all around the world who are fans of that subject.
This particular fanlisting is for fans of Michael Lee from the anime series Witch Hunter Robin. If you're one of them, feel free to join!
Michael is not just another member of the STN-J team. His situation is quite different - as a former hacker who was caught entering the STN server, he had to choose between working for them or death. He definitely is an important team member, though, keeping his eye on the team and helping them with information. Using Wizard as the fanlisting's name has for me two reasons. One, a bit silly one, is a play on the witches in the WHR world. The other, more important one, is that wizard is a word for a great hacker (not a cracker). See here.