Facebook Mentions is an app for celebrities to reach out to their fans and followers through Facebook.
It is "only available to verified public figures", so you'll only be able to use it if you're a big shot actor, singer, athlete, or similar well-known figure. If you are, then you'll find the app useful. You can check what fans are saying about you, share updates and media, and even host live Q&A sessions from your phone.
If you're a star with an iPhone, Facebook Mentions is a must-have app.