Fully expand: Displays all the forum posts in parent/child order. Replies to a forum post are appended as children of that post.
Expand to maximum: Displays the forum posts in parent/child order up to a maximum depth indicated by the value for 'Maximum indent level'. Replies to a forum post are appended as children of that post.
No indents: Displays the forum posts in chronologial order. Replies to the forum are appended to the end of the forum thread.