Are you wondering about the location as where iTunes saves the Apps and data, downloaded and installed by you on your Apple devices like iPhone, iPod Touch or iPad? The apps setup (.ipa files) can act as a good backup or in case you just need them.
Note – All the iPhone applications are saved on your computer if they were downloaded and installed straight using iTunes. However, if the apps are installed directly on idevice using Wi-Fi or 3G, then you must first Sync the device with your system (using iTunes) to find the installation files on your computer.
To locate the Apps on Windows, launch iTunes. Now click the ‘Apps’ option under Library. Right-click on any app and click the ‘Show in Windows Explorer’ link.
The directory where iPhone apps are saved on Windows will now open, and all the apps will appear with an .ipa extension.
Alternatively, you can access setup files of installed apps by opening this directory in Windows explorer.
C:\Users\User\Music\iTunes\iTunes Media\Mobile Applications
To locate the Apps on Mac, launch iTunes. Now click the ‘Apps’ option under Library. Right-click on any app and click the ‘Show in Finder’ link.
Alternatively, you can access setup files of installed apps by opening this directory on your Mac.
Thanks Vinay for Mac related help.