Apple Brings Back iOS App Support in iTunes (Sorta)
The decision to ditch app support in iTunes, the de facto software used to manage iOS devices since their release in 2007, was cause for outrage by certain users who require the App Store functionality. The company explains on its support page that the app-friendly iTunes 12.6.3 is primarily aimed at businesses and enterprise companies who still need iOS app management support in iTunes. iTunes 12.6.3 is available for macOS and Windows machines.
If you're using the app-friendly version of iTunes, you won't be able to follow along with Apple's latest iTunes updates, and iTunes 12.6.3 will maintain its version number until you decide to update the app manually.
Users of the newer iTunes 12.7 can still install the App Store-friendly version, but may need to create a new iTunes library due to the incompatibility of your current iTunes library with the older version. Windows users can hold the Shift key when opening the app-friendly iTunes to create a new library. Mac users can hold the Option key when opening iTunes to create a new iTunes library.
If you don't need it, or don't miss the lack of iOS app management, you're better off just going with the flow and sticking with iTunes 12.7, an app more likely to receive both minor and major updates compared to the app-friendly spin-off.