The new feature allows users to 'remove' a video from the newsfeed so they can keep scrolling through their feed while the video plays on.
Currently only available on desktop versions, the feature is still a work in progress.
In order to use the feature users need to click on the small box inside a bigger box icon. This will result in the video 'detaching' so that it can be dragged around on screen. The video will continue to play until the user clicks into another post.
Sources: The Next Web; Social Media Today.