Here is an extract from the FAQ's on the subject! It should answer your questions.
Private Messages
The administrators of this message board may permit members to send private messages to each other. A private message is not email. Private messages are one-to-one communications that can only be read by the recipient. You can read private messages in your profile section. You can also elect to be notified by email whenever someone sends you a private message (you can set this in your profile). You can also prevent anyone from sending you a private message (also configurable in your profile). Only registered members may send private messages. This option can be disabled by the board administrators.
To send someone a private message, look for the private message icon on a post a person creates. You can send a private message through the person's member profile, or from your Buddy List, if you have added the person to your Buddy List.
Ignore Lists
Ignore lists apply to private messages only. Anyone you add to your ignore list can no longer send you a private message. You can put someone on your ignore list by viewing the member's profile and clicking on the "add to ignore list" link. Private messaging must be enabled on this site in order to use buddy lists.
Buddy Lists
Buddy lists apply to private messages only. Anyone you add to your buddy list is stored in handy location, so that you can easily send the person a private message. You can put someone on your ignore list by viewing the member's profile and clicking on the "add to ignore list" link. Private messaging must be enabled on this site in order to use buddy lists.