A simple guide to navigate the permies forums?

I've searched extensively, and I haven't found a simple guide to navigating Permies forums (fora?), especially with regard to the icons that appear next to the posts - lightbulbs, etc. I'm tempted to click "Set all topics as read" as I do on Hammockforums.net, the only other forum I use, but I haven't figured out how that would change things. I've been reading more or less full time on Rocket Mass Heaters for several days, and deeply appreciate Ernie and Erica's lucid explanations. Calen asked, "Pretty good thread we run here, isn't it?" My honest answer is that it's too soon to tell. Hammockforums.net sets the bar awfully high.

The light bulbs only appear on the "Forums" page.
On each individual page, there are other icons used (shown at the very bottom of the page).

See attachments:

Many thanks, John. Now I'm beginning to see order in the chaos (another lightbulb switched on).