Uncle Arly said:
If you regularly look at a particular news page, or blog - you wil lsee the newer items at the top - yes? Much like CF's homepage with News items.
RSS is a way of having those new items sent to you automatically, so you don't need to log onto the site.
I regularly visit infendo for instance, and joystiq. Instead of having to log into a browser and open both pages (plus all their ads, and older news items), I use an RSS feed to an RSS reader (generally email clients like Outlook, etc will let you set them up). So you read them like you would an email, but it's just the new items as they get added.
As MouseAT said, it's useful for when there are either infrequent updates (so you don't want to be checking every day), or a LOT of updates where you need to constantly keep checking. It also means you can keep up easier on the move, as the feeds are like emails, so smaller and don't require a browser (making them good for smart phones, PDAs and the like).
Does that help any?