From b2evolution manual

[edit] What can I do with User Groups?

User groups are a quick and easy way to give various backoffice permissions to the users on your site. Once you assign your users to specific groups (only one group per user) you can easily edit their access to:

• the backoffice
• specific blogs
• the Stats tab
• the Antispam tab
• the Templates tab
• the file manager
• the Users & Groups tab
• and the Settings tab

[edit] What are the default User Group settings?

The default user groups in b2evolution are:

• Administrators: Users in this group have full access to the entire backoffice installation.
• Basic Users: The default group for new users. They have no access to the backoffice other than what is given to them by specific blog permissions.
• Bloggers: They can view the "Login" link from the main page of their blog, they can also view the Antispam tab and the file manager (but they cannot upload files by default). They also have their specific blog permissions.
• Privileged Bloggers: They can view the "Login" link from the main page of their blog, they can also view (but not modify) all the blogs on the site, the Stats tab, the Users & Groups tab, and the Settings tab. They have full access to the Antispam tab and they can add/upload files to the file manager. They also have their specific blog permissions.

The default permissions for each group can be modified on the Users & Groups tab by clicking on the group name. New groups can also be created by clicking on the "Add group" link.

For more information, visit the Users & Groups tab.