Super Admin
Somebody who has access the sites network administration features and all the other features of the WordPress site.
Administrator
The person who has the access to all the administration features in the site. Once WordPress is installed an Administrator account is created automatically.
Editor
Someone who has the power to publish and manage posts which include posts by other users.
Author
Someone who can publish and manage there own posts.
Contributor
Someone who can write and manage there own posts, but do not have the power on the website to publish them.
Subscriber
Someone who can only manage there own profile.