I've been meaning to write on this for a while now, but just came across a much better job than I would thanks to Rob Drury. So I recommend you check out How to Explain RSS the Oprah Way.
The quick and dirty is that RSS (along with its close sibling ATOM and others) is technology that enable you to find out what's new on the websites you're interested in without having to go to each one and look at every page. It's a real time saver. I use Google Reader and readlly like it, but there are a lot of other options discussed in the article I linked to.
Almost everything on NWMCmission.org is available through RSS. Just look for links with RSS or Atom in their name, usually on the right sidebar on blogs. The forums also have a link that looks like this picture 
at the bottom of them. You can even subscribe to RSS feeds for the photo galleries, but they're buried in the source code. Ask me if you want to know how
Have more questions? Post them as a comment below.