Wondering what each of the user groups are and what they can do?

Here’s a brief description from the WordPress documentation (Roles_and_Capabilities)

Super Admin – Someone with access to the blog network administration features controlling the entire network
Administrator – Somebody who has access to all the administration features
Editor – Somebody who can publish and manage posts and pages as well as manage other users’ posts, etc.
Author – Somebody who can publish and manage their own posts
Contributor – Somebody who can write and manage their posts but not publish them
Subscriber – Somebody who can only manage their profile

For some Lessons on using WordPress check out WordPress Lessons

For More in-depth documentation visit the WordPress Codex site