I just started the Gopnik article, but I also enjoyed the one by the guy who can't smile. And, as I said earlier I think, the Malcolm Gladwell review of Stephen Brill's book.
But I'm supposed to care what a meme is? 
Yes, because it's much much simpler and it's information that almost everybody you know, at least those of your age or younger, possesses. The chances that it will come up in a conversation with the expectation that you'll know it are much greater. And you could google it in a quarter of a second.
But here, I'm happy to explain once again.
A meme is actually an old sociological term for a thing that gets repeated throughout a culture (or something like that). In the modern sense, it's just some thing -- usually an image or a saying -- that gets repeated in different forms on social media and elsewhere. Usually, for example, it will be one picture with various captions, or a picture that's been altered in different ways. Or it might be a famous quote presented in different contexts.
So remember that cop who pepper-sprayed the protesters at the University in California? That image was widely memed. Here are a couple of pages of examples:
http://knowyourmeme.com/memes/casually-pepper-spray-everything-cophttp://peppersprayingcop.tumblr.com/These are more elaborate and creative than memes usually are, but you get the idea.
See, that wasn't so hard. Now you can go back to forgetting it.
