With this new feature, your content editors will get a better overview of the usage of various media items (images, pdfs etc.) across the created content. This makes it easier to do editorial changes based on the media items used, without having to search through all content or remember where you’ve used your media.
A Request For Comments has been accepted on this topic on GitHub. You can see it right here
Released on the 31st of March as part of the Umbraco 8.6 release.