This will come in handy for users who have more than one person at home, or who have more than one person who watches Apple TV. Presumably this means that users can have their own set of preferences, TV shows and movies that they have saved, and so on. It has been speculated that because of this, it is possible that maybe iOS 11 could include a similar multi-user feature as well.
However given that smartphones aren’t really shared, we’re not sure if such a feature would be so useful. As for picture-in-picture mode, it should function similarly to how the feature works on other TVs, where users could have a video open, and have another video open and playing in a smaller window docked to the side, or maybe have an app running while a video is playing.
Apple’s iPad already offers up something similar so it makes sense that the feature would arrive on tvOS as well. In any case take it with a grain of salt for now, but with WWDC 2017 kicking off in the next couple of months, we should have the official details soon.