How to add and edit user roles in WordPress
From the admin panel of your WordPress you can register new users. You have to assign a user role to each registered user. The user role defines what the user is allowed to do and what settings they are allowed to configure. By default, WordPress comes preconfigured with several user roles: Admin, Editor, Author, Contributer, Subscriber. Each has its set of permissions.
WordPress doesn't have any in-built options for creating new user roles and for editing the permissions of existing ones. To do this you need a suitable plugin. There are some that are ideal for the job. One such convenient and easy to use plugin is User Role Editor. Another similar one is Advanced Access Manager; in addition to adding new roles and editing existing ones it also provides options for limiting accesses to particular sections of your site (e.g. posts, pages, etc.).
For detailed information on registering and managing users read the tutorial on how to manage users in WordPress.