The Collaboration Tool allows the Instructor and the students to participate in real time lessons and discussions and also view archives of previous Collaboration sessions. The Collaboration Tools can be used to hold real-time, office hours and question/answer forums. Guest speakers can be brought in using the Collaboration sessions.
The discussion board is similar to a listserv in that it is asynchronous. An instructor can create different discussion boards for different topics and use the discussion threads for a portion of a students grades. It is also possible to make the discussion boards anonymous if you are teaching a particularly sensitive topic, but want to encourage interaction.