RSS stands for Really Simple Syndication.
Basically it's like news feeds for your favorite web sites, but without actually having to go visit them. Using a "news reader" you "subscribe" to a bunch of sites, and then when new content is published/posted you'll see the updates in the news reader. Many people who blog and read others blogs use them to check for updates. It's a lot easier to check one program than it is to open 10, 20, 30+ web sites.
I like to use bloglines.com as my news reader. This way no matter what computer I'm at I can check my rss feeds. Plus it's free and has many of the same features of some of the locally installed programs that I have used in the past.
Here is a description I found on the web in case that made no sense what-so-ever:
With all that said... I find message boards hard to follow in an RSS feed, but if you were just limited to Amber Alert forum then that would be beneficial to get the updates quickly. A seperate feed for each forum may not be bad either, but at that point you might as well just visit the site.
edited: whoops... I didn't see GWD's post before I posted the above...