* Administrator – Somebody who has access to all the administration features
* Editor – Somebody who can publish posts, manage posts as well as manage other people’s posts, etc.
* Author – Somebody who can publish and manage their own posts
* Contributor – Somebody who can write and manage their posts but not publish posts
* Subscriber – Somebody who can read comments/comment/receive news letters, etc.
via http://codex.wordpress.org/Roles_and_Capabilities