A fanlisting is simply an online list of fans of a subject (in this case for neasala) that is created by an individual and open for fans from around the world to join.
There are no costs, and the only requirements to join a fanlisting are your name and country. Fanlistings do not have to be large sites (although some are), they are just a place where you can sign up with other fans. TheFanlistings.org is the original (but not official) web directory for fanlistings, dedicated to uniting the fans.
Description from tfl.

Neasala is the Crow King of Kilvas, the smallest country in the continent and peraphs also the poorest one. He might appear as a cruel, egoistic person, but instead he deeply cares about his country and his people and he's ready to do everything possible for the wellness of his citizens (making business with corrupted beorcs, pirating, becoming ally with the Dain Empire and such). He's Reyson best friend (although he betrays him, in a particular way) and him and Learne are probably the only "strangers" he cares about.