What is a fanlisting?

A fanlisting is just a list of fans. A perfect example would be this fanlisting, dedicated to pugs. All we're doing here is listing people who proudly call themselves fans and would like to have their name on a list, or possibly display a button on their website to profess this level of fanishness. A fanlisting is made solely for fun; it costs nothing to join (besides a minute to fill out a form).

But what's the point??

To have fun! :D
To see how widespread the fandom is. Yes, some of us are bored enough to want to see if anyone in a random country like New Zealand likes pugs. ;)
To show how that you love something. Now, just because you don't join a fanlisting for something doesn't mean you aren't fond of the subject. I myself am a fan of cheese, but I don't recall joining its fanlisting. But it is fun to go to someone's website and look at the fanlistings they've joined; they're just representations of all your hobbies and favorite things in the form of tiny pictures. Again, it's just for fun.

I don't blame you if you don't fully understand yet, since when I started out I was terribly paranoid (especially about my email address getting spammed). You can always check out The Fanlisting Network's TFL For Newbies page for a clearer, better understanding of what they are.