Android 8.0 Oreo users now get Picture-in-Picture mode on YouTube TV through the application's latest update, something which could be pretty useful if you use the streaming service and are wanting to continue watching a live TV program but also may want to multitask and take care of something else at the same time. Just like with YouTube the Picture-in-Picture mode is activated when the user presses the home button on their device after starting a video in YouTube TV. At this point the app shrinks down to a small video window which stays open atop all other open apps, allowing you to launch anything else on your device and keep the YouTube TV program going above it.
This is part of YouTube TV's v1.11 update which should already be rolling out to users as of earlier this morning or earlier this afternoon, though keeping in this in mind it's not guaranteed that all users will have the update already or even by the end of the day as sometimes updates can take days to reach every single user. If you like the idea of this feature being available within the app it appears to be automatically enabled, though it is possible to disable it using a toggle within the app's settings menu if you'd prefer it not be on. The toggle is pretty easy to find as it's listed under a menu label that says "Allow Picture in Picture," so naturally tapping this toggle would turn the feature off. You'll also find this option under the Picture in Picture sub-menu, which can be found as the bottom-most option in the regular settings menu of the app.
This seems to be the only noticeable change for the app as part of this update though usually updates will also include things like bug fixes and performance improvements to help make the app run smoother for users, and although these changes aren't listed it's likely that they were implemented as they are under the hood changes that users won't generally notice right away, if at all. If you haven't seen the update come through to your device yet you could always try hitting the refresh button on the app updates screen, and if you haven't given YouTube TV a try yet you can grab it from the Play Store button below.