Users and roles
Drupal allows an unlimited number of user accounts—site users each with a unique username, e-mail address, and password—and it employs roles to which you can attach permissions. A site user's capabilities are dictated by the role(s) the user is a member of and the permissions that are assigned to those role(s).
Each role, including the special Anonymous and Authenticated user roles, is granted one or more named permissions allowing them to perform certain tasks.
A list of the currently defined roles is found by navigating to People | Roles (admin/people/roles):
Here, you'll see a list of the roles available on your site by default:
Let's see how these roles are defined:
Anonymous user: This is anyone who is not logged in, that is, public visitors to your site
Authenticated user: This is used for logged in users
Administrator: This is a special Drupal role that is granted a high level of permission—often dangerously high for many users and really only meant for senior site administrators...
