The Discussion Board is a tool for sharing thoughts and ideas about class materials. The main Discussion Board page displays a list of available discussion forums that may also be linked in other areas of your course. It will also provide you with information such as the forum description, total number of posts in each forum, number unread posts, and total number of participants.
A forum is equivalent to a discussion topic - an area where uses discuss a topic or a group of related topics. Each forum contains discussion threads - which consists of an initial post/message and any replies to that post.
Note: Your instructor controls which tools are available. If this tool is not available, your instructor may have disabled it.