Explainer Chart

Discussion Boards are organized web pages that provide people who have a shared interest with a way to discuss topics related to that interest. 

They are organized as shown in the diagram below.

Categories and Forums are set up by Administrators (black rectangle above)

Users (members) can add Topics and Replies to the Forums (green rectangle above)

A Discussion Board can have many categories and each category can have many forums. Each forum, in turn, can have many topics. And each topic can have many replies.