Popcorn makes video work like the web. We create tools and programs to help developers and authors create interactive pages that supplement video and audio with rich web content, allowing your creations to live and grow online.
via Mozilla Popcorn – Making video work like the web. The video at the link makes it a little bit clearer. The concept is basically at points in the video you can load in data from the web about the video or what’s shown in the video from Twitter, Wikipedia, Google Maps and other stuff.