This wiki has multiple user groups that allow users to perform different privileged actions.
The full list of groups and their rights are at Special:ListGroupRights.
Users
All accounts can edit unprotected pages and create new ones.
Autoconfirmed users
Accounts that have existed for at least 4 days and have at least 10 edits are autoconfirmed. This allows them to edit semi-protected pages and not be affected by rate limits for new users.
Administrators
Administrators (or "sysops") can block users and IPs, use the rollback feature to quickly undo edits, delete and restore pages, view the contents of deleted pages, delete specific page revisions and log entries, edit interface pages (the MediaWiki namespace and other users' CSS/JS), manage translation groups, edit fully-protected pages, mark pages for translation, approve revisions, and use several other features.
Bureaucrats
Bureaucrats can edit user rights (including promoting users to administrator) and rename users.
Suppressor
Suppressors can suppress page revisions and log entries, which hides them even from administrators. This is useful in cases such as personal information being posted.
Bots
Bots are automated user accounts. They can mark their edits as bot edits (hiding them from Recent Changes by default) and have a higher rate limit when using the API.
Abuse filter editor
Abuse filter editors manage filters at Special:AbuseFilter. They can see and edit private filters too.
Translation reviewer
Translation reviewers have access to the review tools of the Translate extension.
Approver
Approvers can approve revisions to pages.