Two stories here. First, Facebook is adding a video app to streaming tools like Apple TV. It is part of their desire to overtake YouTube as the king of online video. YouTube already has an app on things like Apple TV.
Second, when videos appear in your Facebook feed, not only will they play automatically, they will now also automatically play with sound. Until now the videos played automatically, but you had to tap them to turn on the sound.
You can read about it at: