I posted a week or so ago a handout that explained the different User levels (Administrator, Contributor, Author, etc.) on WordPress. If you find that those preset user roles aren’t exactly what you want, no worries, Capabilities allows you to set whatever permissions you want.
You can find Capabilities under the Users menu. There, you can make changes to the preset roles, or even create your own unique user level, name it what you want, and give it the specific permissions you want it to have.