What are the WordPress Roles?

WordPress has 5 role types for its users, as described below.

AuthorGives the user the ability to write and publish their own posts and comment. This is most common for students.
ContributorRequires the instructor to moderate posts and comments before they are published.
SubscriberAllows the user to view content, but not post or comment.
EditorGives someone the ability to publish and manage other users posts.
AdministratorGives the user access to all administration features (the role instructors are given).