There are four different types of permissions:
User/Group permissions (global) - e.g. disallow changing avatar
Administrator permissions (global) - e.g. allow to manage forums
Moderator permissions (global or local) - e.g. allow to lock topics or ban users (only global)
Forum permissions (local) - e.g. allow to see a forum or post topics
Each permission type consists of a different set of permissions and can apply either locally or globally. A global permission type is set for your whole bulletin board. If you disallow one of your users to send Private Messages, for instance, you have to do this with the global user permission. Administrator permission are also global.
Figure 1.6. Global and local permissions
On the other hand local permissions do only apply to specific forums. So if you disallow someone to post in one forum, for instance, it will not impact the rest of the board. The user will still be able to post in any other forum he has the local permission to post.
You can appoint moderators either globally or locally. If you trust some of your users enough, you can make them Global Moderators. They can moderate all forums they have access to with the permissions you assign to them. Compared to that, local moderators will only be able to moderate the number of forums you select for them. They can also have different moderator permissions for different forums. While they are able to delete topics in one forum, they may not be allowed to do it in another. Global moderators will have the same permissions for all forums.
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