What Can I Moderate?: As mentioned there are three viewable forms of interactions which you can monitor. Each can be accessed through the "Posts," "Comments," and "Conversations" buttons respectively. These buttons are located at the top right of the Moderation menu.
What Can I Do?: You have the ability to delete specific posts as well as comments using the "Delete" button on the right hand side of the Moderation menu. That being said, you cannot delete conversations through the Admin.