The registered users of your blog have different rights. Subscriber has fewer rights than any other user of your site. It has the access to the admin panel. But subscriber can’t see all the functions of the admin panel.
He can only change its profile and return to the site, where he can leave his comments. The comments won’t be published until the administrator of the site approves them.
Contributor can post comments and add posts from the admin panel of the site, but they won’t be published until the admin of the site approves them. More functions are visible for him in the left sidebar of the admin panel. This type of user can add tags but he can’t create categories – he can only use the existed ones.
Author can add posts and comments without administrator’s permission. Author can’t edit or add pages but can add media files.
Editor can edit everybody’s posts and comments without the permission of the admin. He can also edit and add categories and pages.
Editor is limited only in managing the functionality of the blog itself. Editor has no access to plugins, to the users profiles, he can not change the appearance of the site or manage other important settings which refer to the functionality of the site.
Administrator role allows to manage the entire site, its functionality and correct work. The administrator has the right to change the code from the admin panel if the files have special permissions. He can approve or disapprove comments and posts of other users and he can also change their roles in their profiles.
Since the administrator is the most important person who runs the blog, it is better not to give anyone such role except for the owner of the blog.