In a post by Fidji Simo, the VP of product at Facebook, “In a Watch Party, members of a Group can watch videos together in the same space at the same time — videos are chosen by the Group admins and moderators, and can be any public videos on Facebook (live or recorded). With everyone watching, commenting and reacting to the same moments together, it creates a shared viewing experience for video that helps build the kind of community and engagement we’ve seen with Live.”
Basically users will be able to watch videos together and comment and react to it at the same time like in a Live video. It does sound like fun and could be handy for work, school, or just entertainment in general. For example videos for work or school can be watched together even if the members are in different areas, and they can comment and collaborate on the topic at the same time.
However at the moment it appears that the feature is currently in testing which means that it isn’t as widely available as it could be yet, but we expect that it should eventually find its way to more users in the future.