An infographic / information graphic is a visual explanation. The point is to visualize some data, information, wisdom, story, etc, into a form that appeals to the visual centers of the brains. A well made infographic, in my opinion, can explain some concepts much better than text.
The kingpins of infographics in my opinion are Edward E. Tufte and Nigel Holmes . You can find some kick-ass examples of their graphics on their sites and even more if you dive into google's image search, I'll make it easy for you, holmes , tufte1 , and tufte2 . Tufte's specialty is in the visualization of data, and he's written a number of books on the subject that are basically famous and required reading -- I almost never buy books but I just picked up "Envisioning Information". Nigel Holmes is more on the side of explaining concepts which may not be so much data but more like stories, like a lot of news stories, various technical concepts and so on.