Feed for Dummies (Me)

So, in the left column underneath the 20 Times a Lady section, I've added "feed" information and links so you can subscribe to this blog and read it in a feed reader, or receive emails when I update. I consider myself pretty computer literate, but all this feed stuff--RSS, Atom, feed readers, etc.--confuses the crap out of me. Now I know how my mom feels when she tries to operate the DVD player.

Can anyone tell me the very basic difference between RSS and Atom? Also, I've been told that I shouldn't have both on my blog--is this true?