The discussion board is divided into several discussion areas so that questions for each homework assignment can be grouped together. There's also a General Discussion category for whatever else people feel like posting. If you would like to receive e-mail notifications of new posts, you can click Profile and then Notifications to set that up.
The mailing list will be used for occasional announcements -- for questions and discussion, use the discussion board. Students should be automatically subscribed to the mailing list within 24 hours of registration, using their @u address.