This is TF's own secret mail club, where members of the TF forum can introduce themselves and then get mail from other members of the forum :). This community is only for fellow TFers. In order to join you must send the user 'rubylips' a PM at TF telling your LJ user name. This, of course, it to protect the personal info people submit to this LJ community :).
There's only one real rule: in order to not be deleted from the community, you must post your introduction with your address as soon as you get approved. If you need help with this, again, you can PM 'rubylips' at TF. It's important that everyone joining gives out their address so that others feel comfortable sharing theirs. So make sure you're prepared to do this as well :).
Other than that, have fun! This community is about bringing joy into the lives of your fellow TFers. You can send anything you like or something you know the person would want to receive. You can do it anonymously (in which case the recipient won't feel like they have to send you something back) or you can identify yourself. But whatever you do, remember this isn't about trading stuff at all, just sending out nice stuff to people you want to surprise and make them smile!