You can make your forum categories open to the public or private. With private categories (like the one you’re in now), you choose exactly who can access them.
Make your categories accessible to:
Everyone. Any site visitor can view the posts.
Members only. People who aren’t logged in will be prompted to sign up or log in to view the posts.
Selected members. Choose individual members, roles, badges or subscriptions.
Members. You can select specific members.
Roles. Allow access for roles you create like admins, moderator or students.
Badges. Create badges your members will strive to get, like “Top Poster” and “Top Commenter.
Subscriptions. Create categories that are only accessible to paying (or free) subscribers. If you have exclusive areas that people want access to, this is a great way to earn money from your forum or grow your membership.
You can also set the visibility of private categories. That is, you can choose to hide “secret” categories from the rest of your members. For example, the category you’re in now is visible only to you, the site owner. Your members don’t know it exists.