A discussion board is a general term for any online "bulletin board" where you can leave and expect to see responses to messages you have left. Or you can just read the board. Bulletin board services were invented for this purpose (as well as to allow for the exchange of uploaded/downloaded files). Most course management packages have integrated discussion board capabilities.

Using a discussion board is quite straightforward. You can retrieve a message by clicking on its hyperlink and then read it online or print it. You usually make a posting to a discussion board in a similar fashion to composing an email.

Follow this link for learning how to use discussion boards in Sharepoint.