I get lots of people ask me about RSS, what is it, why would I use it, and how would I use it. My plan was to write a short primer, but why do that when I can reuse!
Here is an old but good intro to RSS from Lee Lefever from Common Craft, the basic content is still good.
Two things to note the icons he refers to have changed and now typically look like:-
Which is lots better than the mess we use to have:-
Lee, with the help of his wife, has released a great video introduction to RSS.