What do the little envelopes mean...?

Is there a section that explains this?...maybe I am missing it. But I see red envelopes, white ones and so forth what do each mean?

Red ones means there are new posts in that section or thread. And arrow in the envelope means you posted in it. A white envelope means there are no new posts to read.

A "red" envelope means that the thread is a "hot topic"...that it's had a lot of replies to it. A blue envelope is just a regular thread. If the envelope is "closed" then there are no new posts since you last looked at that thread title. If the envelope is "open" with a little bit of paper sticking out...that means there is a new post(s) to see in that thread.

An curved arrow over the envelope means that is a thread you, personally, have participated in. A straight arrow means it has been moved to another forum. And a padlock means that thread is closed and no new posts can be made.

If you look at the bottom of each forum section, you'll see a legend that explains all of the different icons.

Here's a screenshot of the legend, for simplicity :)

http://nathanledet.com/vb_icon_legend.png