In the Newbies section of the forum, there is a thread initiated by the ccboard_admin, that explains what all of the little forum icons mean. That thread is from 2002. In light of the recent changes to the forum, and many more icons, I suggest that a new thread is in order.
Also, if I may make a suggestion, I think some kind of indicator would be nice, to show a user that he/she posted in a thread. These indicators are used on other forums and I haven't noticed one on this forum, if there is one.