There are main five roles you can assign to individuals.
Administrator - An administrator has full and complete ownership of a site, and can do absolutely everything. This person has complete power over posts/pages, comments, settings, theme choice, import, users, and everything else. Nothing is off-limits, including deleting the entire site. Be mindful of assigning this role, unless you have created a group site and are turning control over to someone else.
Editor - An editor can view, edit, publish, and delete any posts/pages, moderate comments, manage categories, manage tags, manage links and upload files/images.
Author - An author can edit, publish and delete their posts, as well as upload files/images. Authors do not have access to modify, add, delete, or publish pages.
Contributor - A contributor can edit their own posts but cannot publish them. When a contributor creates a post, it will need to be submitted to an administrator for review. Once a contributor's post is approved by an administrator and published, however, it may no longer be edited by the contributor. A contributor does not have the ability to upload files/images.
Subscriber - Subscribers are registered users of your site and can read material. They do not have any editing privileges. Subscribers added via the Users page will be able to read material only. They will not be updated when new material is added to your site and the list of users will not show who has subscribed to your site. If you would like users to be updated about material, they must be added as Subscribers using the Subscription plugin.