[a-dam]

If you're in a particular forum, there are those orange-centered "buttons" all the way on the left side. I see that they signify "Hot thread with new posts" and "Hot thread with no new posts".
What are hot threads? Someone stole my pants?

[georgev]

Hi there a-dam!

If you scroll to the bottom of a topic page then you'll find the icons explaining what these icons mean (and I bet you've found these already!).
Hover your mouse over each one for abette explanation!

Hot thread with new posts = More than 15 replies or 150 views

Hope this helps!

[a-dam]

Thanks, georgev. That clears it up. I should have tried the mouseover.