Welcome to the site, Purple! I'm semi-new here as well, and also had that question when I first joined.
From what I've seen, it is a steady community, if not a bustling one. There are probably bigger ones out there that have much more happening, but I think this is one of the more robust sites. At least two major events have happened since I joined, TIG and the Thunderdome, and there have been some minor waves of posting in between. The rest of the time, there seem to be only a few posts every day.
As for navigating, I've found that if you click on "Forums" on the side, then you can see the most recent post in each of the sub-categories. I then go through all those that have been posted in since I last checked, to make sure nothing is getting covered up.
TL;DR: It's a robust community that gets bursts of activity. Click through the forums and check out what has been posted since you last checked.
I'll leave it to the more experienced ones to explain it all better, lol.