There are four roles: Administrator, Editor, Author, and Contributor. :))
Administrator
The Admin can do everything. Complete power over posts, comments, settings, theme choice, import, users – the whole shebang. Nothing is off-limits, including deleting the entire blog.
Editor
They can publish any posts, edit any posts, edit any published posts, edit any pages, moderate comments, manage categories, manage links and upload files. They can also delete any posts and any pages. They can read, edit and delete private posts.
Author
Is able to edit their posts, publish their posts and upload files. And they can delete their posts too.
Contributor
They can edit their posts but cannot publish.
Extra Advice
Be careful what roles you give people, especially if you want them to be an Editor or joint Administrator – Editors can delete content, and Administrators can remove users, including you. Promoting someone is easy – removing a role is much harder.
Daniel Voyager 
good news.
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Daniel, I appreciated finding your simple roles description as the WordPress write up was much more than I needed. I’ve borrowed from this post (have tried to give you credit but don’t know how to link to you here).
I also wanted to let you know there is the 5th, subscriber role, which most blogs require people who want to comment, to register.
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