The standard DotNetNuke forums module has the ability for users and visitors to start threads and reply to other people's threads. Depending on the member permissions, they can post replies to existing threads, start new threads and moderate forums. The forum administrator has the ability to manage forums and threads, assign and delegate privileges to other forum members.
The forums module also supports features like User Banning, Direct Post Links w/ Anchors, Admin/Moderator/User Control Panels, Forum RSS, Multiple Attachments, Inline Post Image Attachments, Thread Bookmarking, Limiting Post Edit Period, Search Keyword Highlighting, view latest threads and many more.