Background play is just the audio no? I mean the actual video staying on screen as you switch between apps.https://twitter.com/TeamYouTube/status/1186497032187453441 …
Good question! Background play allows you to play videos on your mobile device while using other apps or when your screen is off. Picture-in-picture is a different feature and it's available on certain devices. Learn more here: https://yt.be/help/5zw4 . Hope this helps clarify.