For years, iTunes has had a Home Sharing feature, that allowed you to share your library across a network. Users in your home, dorm, or office could listen to your music, and even copy it to their computers. They could stream videos from your library, and this was a good way to maintain a movie and TV show library on a Mac and stream content locally to an Apple TV.
Perusing macOS Catalina I was initially worried that Home Sharing had been removed, because there was nothing about it in the Music app, but I found that they feature had been shunted to a new location: the Sharing pane of System Preferences.
This makes a lot of sense. With iTunes split into four apps, you wouldn’t want to have to turn it on for each app. But this centralized media sharing has a great advantage: you don’t need to launch any of the apps to be able to share their content. As long as the computer hosting the media is running, you can load its content on another computer, an Apple TV, or on iOS (in the Music or TV apps). And if you have Wake for Network Access checked in the Energy Saver preferences, your library is accessible even if the host Mac is asleep. (On a laptop, this only works if it’s connected to power.)
This is a great change to the Home Sharing feature, and it will make it a lot easier to set up a master library to use on multiple devices.