This isn't actually a built-in Windows feature but rather a new app that shows off some Fall Creators Update capabilities. Story Remix can intelligently craft a video show for you using the Microsoft Graph. It lets you do things like changing the video to be about one of your contacts or adding 3D objects from Remix3D.com. Microsoft showed a very cool demo of a 3D fireball object actually following a soccer ball and exploding at the goal. Story Remix also lets you write on top of video, and your writing can follow an object in the movie. For more, see my hands on with Story Remix at Build.