Phabricator is Miraheze's task tracking system. While most tasks on there require a system administrator, some don't. A user might need help enabling an extension or might have not been able to find a setting in ManageWiki. In these cases, if you know the answer, you're more than welcome to reply to the task. In some cases, if you are certain that the issue has been resolved, you can close the task. If you're new to Phabricator, it is recommended that you wait and learn what types of tasks are closed when, to prevent you from accidentally closing a task that hasn't actually been resolved.
Even if a task involves something technical like importing a database dump, you can still help on the task by sorting the tags correctly for the task. For more information on tags, see Phabricator.