It’s essentially Facebook’s equivalent of YouTube’s Content ID, albeit focused more on managing copyrighted video content uploaded to the social network and tackling infringement, rather than monetising user uploads of it.
The Rights Manager tool will enable rightsholders to: “Easily upload and maintain a reference library of video content to monitor and protect, including live video streams; Specify permitted uses of each video by setting match rules; Identify and surface new matches against your protected content so you can review them and file a report if needed; Whitelist specific Pages and profiles who have permission to use your copyright content; and Outsource management, monitoring and protection of your content by using our Rights Manager API” according to Facebook.