As you may have heard last week, Apple will be discontinuing iTunes. When they release macOS Catalina, they will have three new apps to take the place of iTunes: music, TV, podcasts. No longer will you be able to use all three in one app. You will still be able to access everything you have in iTunes via these apps. iCloud will still sync everything across devices as well.
Apple music will also be able stream music on your Mac through the music app. The TV app will have movies, shows, and premium channels. They also say Apple TV+ is coming soon. You will be able to listen to your podcasts with the podcast app. Since it can sync across your devices, you can start on one device and finish on another.
Other things new that will be coming with the new OS is a rebuilt Reminders app. You will be able to add attachments to reminders. The start page will have an update and will add Siri Suggestions. There will something called Sidecar that allows you to use your iPad as an extended screen. You can work on one and display on the other or mirror the screens. Also with Sidecar, you will able to use the Apple Pencil to work on supported apps. Screen Time is also going to be available on Mac. There will also be enhanced security on the Mac. There are accessibility enhancements such as Voice Control, omm the second display, Hover Text to make some text larger and more readable.
Watch the WWDC 2019 Keynote from Apple: