In WordPress each user has a difference role.  A role defines what each user is able to do on a website.  The roles which can be selected are:

• Administrator – capable of changing everything in a WordPress site and managing all other users.
• Editor – Has access to all of the content within a WordPress site, without being able to administrate it.
• Author – Can create and publish content for a WordPress site, and can manage content, but only content which they have provided.
• Contributor – Can contribute their own content to a WordPress site and edit content they have provided, but cannot publish it.
• Follower - Can view and comment on content within a site.

You can change a User's role at any time by going to Users ->  All Users.  Mark the Check box beside the User you want to edit and then select Change Role To... and select the role which you want the User to have within your site.