What is difference between RSS and Atom and how do they work?

What is difference b/w RSS and Atom. I use Firefox and see an orange icon in address bar whenever i access some password protected site? does that mean every password protected site, like yahoo and gmail and hotmail, are RSS and Atom enabled?

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I do not know the difference between RSS and Atom, however, they are not security-related. They are types of news feeds. Clicking on the orange icon will allow you to subscribe to the feed from that particular page.

I believe Atom is a newer type of feed with more features than RSS, but I'm not sure.

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