The Little Black Book
No, this isn't a place for you to keep all the names and numbers on your bedpost, at least, not unless you want to do it this way.
This forum allows all players to create generalized threads for their characters, allowing others to get introduced to them, as well as post in those threads requesting play, talking about them, asking questions, or just messing around and spamming; we're not picky which.
Each character gets their own thread. However, if you would like to consolidate all of your characters into one thread, that's not a problem. Alternatively, you can also share a thread with a friend or two, and if you have a character that naturally groups with another, this is probably a smart idea. On the other hand, since you already get a forum for
groups, it may be more beneficial for you to just dedicate a thread solely for your character.
As mentioned, we don't really care for what you use it for. Some people like to get a bunch of replies for the sake of getting inspiration and meeting new people to play with. Some people prefer to use them to keep track of character relationships, threads, and plots more centrally. Do whatever you like with these threads; design them how you please; they're yours.