Change Div background image and content on link hover?

i've looked around a bit but most of the solutions are specific to the links background, and not the div's background. I'm trying to understand how to image swap backgrounds for an entire div by hovering over a link in that specific div.

By visiting this page: http://splash.org/, and scrolling down to "Today we served" section, you can hover over the content there and the background image will change.

Thanks!