They use simple e-mail as the vehicle for the conversation. Users join the list by sending an e-mail message to a specific address. Any message sent to the list is automatically sent to all members. As a result, all members can see what everyone else is saying about the topic of interest. Using this basic technology, discussion lists facilitate communication with a large group of colleagues simultaneously.
Forums provide a graphical view of a class discussion.
For example, Professor Jones teaches English 101. She enters all the e-mail addresses of the students in her class and saves that list with the nickname eng101. Later in the semester when she wants to remind her students that class is cancelled for the next Friday, she can send one message to nickname eng101. All of her students will receive the same e-mail message. If any of the students answer the message it will go directly back to her - not to the others in the class.