The joining of various media — pictures, video, animation, sound, graphics — and then responding to users is a relatively new concept. Last century it was called "multimedia," then "new media," and then "interactive media." More recently it might be a "Mash-Up" or a "Transmedia Event." But the way people encounter stories and messages has forever changed.
Responsive web design takes into account the device a user is using and customize the content to suit the device. On a mobile platform it can even customize the presentation based on the user's location.