Okay you have to be a bit of a geek to be asking this. It’s the way the theme utilizes some of its built-in slider plugins. There is an option to add customized css as a theme option that will also add this effect, but I prefer to put this into a ‘child theme’ style sheet; that way it’s not littering the page. Many users of this theme have made a request to move the styles off the generated pages, so hopefully that will be fixed in a future update.