Simple definition
A WordPress role groups capabilities that determine what a user can do.
Purpose and use
A WordPress role groups capabilities so users can receive a defined permission set.
How does it work?
Built-in roles provide a starting point, while plugins or customization can add roles and alter their capabilities.
Example and verification
During an access review, examine effective capabilities and user needs before granting a broader role.
Points to watch
A site administrator role is not server-administrator access to hosting. Multisite introduces additional levels and constraints.
In short
Roles simplify permission assignment; their contents should remain aligned with tasks actually required.