What is an "editable role" in WordPress?

WordPress core has the ability to hide specific roles from other, high-privileged users. These roles are referred to as "not editable roles". When a role is designated as not editable, it will not appear in the "Role" drop-down list on user edit screen, preventing them from promoting or assigning anyone to that role.

This feature, provided by the WordPress core team, is further enhanced by the AAM plugin. It enables administrators to completely hide these roles from the "All Users" page as well.