If the iTunes app is open, your Mac will tell you that the installation can not proceed until you close iTunes. You no longer can buy an iOS app within iTunes, and then load the app to your device when you perform a sync.
One could say that the iTunes is still doing more than what it should be but there has been a rumor for a while now that iTunes could be going away in the future in favor of separate apps for music, movies, podcasts and TV shows on the Mac. And the new App Store makes it easy to get, update, and redownload apps - all without a Mac or PC.
While Apple might be aiming for convenience and streamlining iTunes management, some users in Apple's discussion forums don't appear to happy with the decision.
With the iTunes version 12.7 update, Apple has removed the built-in App Store and the Ringtones section from app. Click Continue to have your Mac close iTunes and continue with the upgrade.
When opening iTunes 12.7 for the first time, users will be greeted by an update prompt from Apple.
Downloading and installing iTunes 12.7 should only take a few minutes, but this will depend on the user's internet speed.
With Watch OS 4, you'll be able to see your heart rate right on your watch face. You can also look forward to the new Files app, customizable Control Center, Voice translation, new app switcher, improved Live Photos and Portrait Mode, and slight tweaks to the UI design. Games and Apps on the new iOS 11 App Store will be more informative with support for more video demos, app ratings/rankings and age rating.
Interestingly, iTunes v12.7 update also brings in the ability to sync iOS 11 devices, as well as the ability to discover content with friends on Apple Music much easily.