Here is an overview of the most important user roles
Subscriber
This is the standard role. This is for all the users that are supposed to only have access to the course as a participant (front-end).
Course Facilitator
This user has access to the courses, but also all the Simplylearn functionalities. The facilitator can, for example, create courses and give feedback to the course participants' assignments.
Admin
This user has access to all functionalities. In addition to what the Course Facilitator can do, an admin can for example add users and control various settings.