One of the many features available to WordPress administrators is the ability to create new users who can add, edit and delete information. While having a site where multiple users can modify content is a wonderful thing, it is important that the administrator have the power to control which parts of the site the other users can edit. This is where Roles and Capabilities come into play. The default Roles in every installation of WordPress are: Administrator, Editor, Author, Contributor and Subscriber. Each of these roles has a predetermined set of capabilities. Please visit the Codex for informative charts. If you find that the default roles and capabilities do not fit your needs, I suggest that you look into the Members plugin by Justin Tadlock.