What do the symbols next to thread subject lines mean?

[PanicAtTheCostco]

(Forgive me if this has been answered before, but I couldn't find it anywhere on this site.)

Okay, you know how on the forum pages every thread subject line has a little paper/pencil symbol next to it? I've noticed that sometimes the pencil won't be there, or it will have a red dot or a green dot, or there are probably some other ones that I can't think of off the top of my head. The only one I've been able to figure out is the padlock to signify a locked thread. What do the other symbols mean? I've been curious!

[Edited to correct a typo]

[Thanksforallthefish]

I believe pencil means you haven't read it yet, no pencil means you did, green dot means you were the last to post, red dot means you have posted on that thread in the past but you are not the most recent.

Let me know if that matches your experience.

[Thanksforallthefish]

Update: Green dot must mean you posted to it and you've read up to the latest comments vs red dot which means you posted to the thread but there are new comments you have not yet read.

[PanicAtTheCostco]

Thanksforallthefish:

That seems to match my experience! Thanks!