At least one person has found that post unclear. So, in even simpler terms:
RSS feeds show you what’s new on a website whenever something new is put on that site.
An RSS aggregator lets you see the RSS feeds for all your favorite websites by visiting just one website.
This is why, right now, I can see that of the 80-odd websites I like to read on a regular basis, 26 of them have new articles. I can find that out by checking one website (my NewsGator account) instead of checking all 85 to figure out which ones have updated. And I can also check to see the titles of the articles before visiting the sites, so that I can skip the ones that don’t interest me.
I hope that’s clearer this time. And again, I hope it helps someone to make better use of their time by streamlining their web surfing.