What do these symbols mean?

PD Power

New member
The new forum has some symbols I do not understand.
What does the little 3 connected dots stand for, in front of some sub-threads.

Also, what do the differing colors stand for, blue, grey and I think, pink, indicate on the various responses?
Icon Legend
Contains unread forum posts
Contains no unread forum posts
Forum is a category
Forum is a Link
goto bottom of this page http://karting.4cycle.com/forum.php to see the main icon legend ( the ones I listed above ) then goto any main section, lets say the subscribers area, at bottom of that page has the thread icon legend that lists a blue envelope is a thread containing new post/unread posts, pink is a hot thread with no new/unread posts etc