For video, see User Roles.
A User Role can be simply defined as “what a user can do" and each User Role is made up of a collection of Permissions. A Permission is a specific activity type or behavior that can be checked for "On" or unchecked for "Off" for any Role. A checkmark indicates that Users assigned to this role are permitted to take the defined action. No checkmark indicates that Users assigned to this role are restricted from taking the defined action.
Let’s assume you wanted to have a custom User Role called “Generalist” and you wanted users with that role to be able to fully process applicants but not Post Jobs. In that scenario, you would only enable all checkboxes within Applicant Tracking and Processing and exclude all checkboxes from Jobs & Templates. Now, any User that you assign to the Generalist Role could process applicants but not create job templates or post jobs.