This application is created by extending built-in liferay Message Board portlet. In built-in portlet, all the categories are always visible to the user, if he has permissions. In new Discussion Board portlet, Administrator can choose the root category for the portlet instance. This can help admin to keep different type of discussion boards in the same site. e.g. In Travel related site, admin can display two different discussion boards for "India places" and "USA places" on two different pages, by selecting respective root categories in both portlet instances. This root category setting is per-instance based.