Roles define what users can or cannot see and do in your Moodle system. Moodle comes with a number of predefined roles—we already saw Student and Teacher—but it also allows us to create our own roles, for instance, for parents or external assessors.

Each role has a certain scope (called context), which is defined by a set of permissions (expressed as capabilities). For example, a teacher is allowed to grade an assignment, whereas a student isn't. Or, a student is allowed to submit an assignment, whereas a teacher isn't.

Okay, so what is a context? A context is a ring-fenced area in Moodle where roles can be assigned to users. A user can be assigned different roles in different contexts, where the context can be a course, a category, an activity module, a user, a block, the front page, or Moodle itself. For instance, you are assigned the Administrator role for the entire system, but additionally, you might be assigned the Teacher role in any courses you are responsible for; or, a learner will be given the Student role in a course, but might have been granted the Teacher role in a forum to act as a moderator.

To give you a feel of how a role is defined, let's go to Users |Permissions, where roles are managed, and select Define roles. Click on the Teacher role and, after some general settings, you will see a (very) long list of capabilities:

We will deal with all this in greater detail in Chapter 6, Managing Permissions – Roles and Capabilities, so don't panic!

For now, we only want to stick with the example we used throughout the chapter. Now that we know what roles are, we can slightly rephrase what we have done. Instead of saying, "We have enrolled the user participant01 in the demo course as a student", we would say, "We have assigned the student role to the user participant01 in the context of the demo course."

In fact, the term enrolment is a little bit of a legacy and goes back to the times when Moodle didn't have the customizable, finely-grained architecture of roles and permissions that it does now. One can speculate whether there are linguistic connotations between the terms role and enrolment.