Through the roster features, the course director controls each user's access level (there can be many course directors).
Because users with different access levels sometimes see different things on the same page, there is a utility which allows a course director (or an instructor or a developer) to temporarily "lower" their access level. This allows a staff person to be sure of exactly what another type of user sees. E.g., a course director can choose to (temporarily) be a student, an instructor, or a developer. And a developer or an instructor can temporarily be a student.
Scheduled for implementation in 1999 is the capability to completely control who has access to each and every utility. For instance, a head TA might be given access to all course roster functions, whereas other TAs would not have this capability.