The User Guidelines in word press chat.

Visitor can submit your doubt about word press working (Like themes ,tags,settings,widgets,plugins..etc)

Author

In WordPress the 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

In wordpresschat the contributor can update 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.

Thanks