Drupal is a role-based application. Different users will be able to perform different tasks in Drupal based on their role in the site and the permissions assigned to the role in the site. The site administrator has the ability to add/change/delete roles in the site. In the University’s standard installation of Drupal, there are 5 default roles defined. You can find the list of default roles in the Knowledge Base: http://it.umn.edu/drupal-definition-user-roles It is incredibly easy to create more roles and/or tweak the roles that are defined. For questions about your particular site, contact your site’s administrator for the details.
In addition to the defined roles in that Knowledge Base article, there are two additional implied roles:
Unauthenticated User: any random person that is viewing your site
Authenticated User: someone at the University that has logged in to your site
Neither of these roles will have any permissions to perform actions on your site.
If you are a site builder, you’ll find more information about users, roles and permissions in the Drupal self-help guide - http://it.umn.edu/self-help-guide/drupal - in the section Add Users to Your Site