Roles

Contributor: As a contributor you can create new revisions to content that you have access to. If new content is created, the ownership and approval falls to the owner of the folder that the content was created in. Any new content or revisions to content that is made by a contributor must be approved and released by the primary contributor. You cannot make new templates and navigation bars, but you can edit the existing templates and navigation bars. 

Primary Contributor: As a primary contributor, you have full access to all content to which you have ownership on. You have all the abilities of a contributor, plus the ability to approve and release content. On content that is not owned by you, you can act as a contributor to the content, meaning you can makes changes to the content and create new revisions, but it must be approved by the owner of the content. You can make new templates and navigation bars, and you can edit both as well

Administrator: Otherwise known as a super user. You can do anything that a contributor and primary contributor can do plus you can perform all administrative duties. As an administrator, you have access to the site administration, user administration, group administration, image administration, style administration, style admin, javascript admin, system error folders. On content, templates, and navigation bars, you act as primary contributor for all. Meaning, you are the owner to all content, templates, and navigation bars.