Contexts
Contexts are the "areas" in Moodle where roles can be assigned to people
They are arranged in a hierarchical fashion, with permissions inherited from "higher" to "lower" contexts.
- System (the entire installation)
 - Front page (the "site course")
 - Course Categories
 - Course Sub-categories
 - Courses
 - Blocks and Activities
 
See also Roles, Permissions, Assign Roles and Overrides.