What's the meaning of circular topic icons?

What do the circles on the left of each topic & post mean? Some are red, some blue, some animated, some have stars in them, some have arrows, some have the letter “i”. Lightbulb icons seem to have some special status since they’re always at the top of the list, but what do the various circle icons mean?

Thanks.

I don’t have a list of every single icon in my head, so I might miss a few, but briefly: red/orange means you haven’t read it. You can click the small orange rectangular icon in the title of the thread to jump to the latest post you haven’t yet read. Blue means you’ve seen it; it hasn’t been updated since your last visit. Scrolling animation means it’s a “hot topic”; lots of people have posted or read it in a short period of time. The little lightbulb shaped ‘!’ topics are Sticky. Nothing special there; except that they stick to the top no matter what—only moderators can create those; we use them for special notices and the like. The little asterisk in the corner means you have posted in it at some point; so it’s useful to scan orange-asterisk for responses to your messages.

There are also Announcement style messages; again a moderator-only style of message. They are set apart from the main list of threads, so even more obvious than stickies.