Project role versus job role

A job role is a security object: it determines which pages and functions you can reach anywhere in the system, and an administrator grants it. A project role is a project object: it determines your part on one specific project team, and you get it by being added to that team. Both exist because the same person can be project manager on one project and a team member on another without their job role changing. The entire source of the confusion is that some names exist as both — "Project Manager" is a job role and a project role — and the lesson says so explicitly, because you will hit it.