Roles and capabilities
From MoodleDocs
Moodle1.7
Roles and capabilities in Moodle 1.7 onwards provides great flexibility in managing how users interact. Prior to Moodle 1.7, there were only six roles possible: guest, student, non-editing teacher, editing teacher, course creator, and administrator. Whilst these roles may still be used, it's now possible to create additional roles, and to change what a given role can do in a particular activity.