They are, as I understand it, employed as tutors. We buy our textbooks, pay for the course, etc. They're there to ensure we learn it and have practice. They devise activities, help with pronunciation, spellings, colloquialisms.

It's worth noting that our final exams are given by a professor from a nearby university. Other than that, she's the only teacher we've got. But no, it's not continuing ed., it's an accredited course.