This is a new generation of forums and communities. You can use this layout for any kind of discussions, especially for support forums, support tickets, product reviewing discussions and thread oriented forums (small number of categories and forums, even just one forum). Below you can find more about main features of this forum layout.

The name of this layout says that topic posts are threaded and designed to display discussions based on post-replies hierarchical tree. This layout makes it easy to follow the discussion flow. Replies are nested from the left side, and you can see the current reply level. Also, you can see the  whole thread of current reply with an informative schema (thread breadcrumb) in each one individually.