There are several type of boards/sub forums based on access method.

Member Only
There are some boards/sub forums which are accessible but only registered member can read/view it's contents.
Unregistered visitors/guests can only browse the topics list and see the topic title. Once you click on a topic title, you will be asked to log in or create a new login account.

WP Manga Users
There are some boards/sub forums which are only visible and accessible for WP Manga Users.
Find this topic for more information http://forum.xhanch.com/index.php/topic,18.0.html