Tech: Icons

Those icons on the left of the page, just under the header "TOPICS". Can someone please explain, or link to a page that explains, the meaning of all the different forms they take. Why, for example do some of them scroll, have different colours etc?

I'm guessing that the heart and star I can see on some of them is determined by the topic icon I can select on the post new topic page, and am going toconfirm this by selecting the "?" icon.

Ah. I see the red star has nothing to do with the icon I select.

In the default skin, the icon is red if you haven't read it yet. It scrolls if it's a "popular" topic (more than 30 something replies). It adds a red star if you have posted in that topic.

Thank you, Cynthia! Yes - I have the default skin.