One issue that sometimes confuses Knowledge Base contributors is knowing what levels of permission each user group on SUMO has. For instance, someone may be able to edit one category or articles, but not another. We now have documented it in a Group permissions page, which you can find linked on the Contributor Home Page.
In short, if you are registered you are considered a contributor. The Approvers group are contributors who have reached the point where they can be trusted on the system. The locale leaders group are contributors who are in charge of the support localization effort for a specific locale.
As part of our response to localizer feedback, we want to make sure the differences are listed and available for everyone to see. If you have any questions or suggestions, please comment on this blog post or in the Contributors forum. Thanks!