What does .ipa stand for? What does the .ipa file extension (used for iOS app bundles) stand for? I'm guessing that it has something to do with iPhone app, but I'm not sure.
Your guess was correct.

.ipa stands for iOS App Store Package

Each .ipa file is compressed with a binary for the ARM architecture that can only be installed on iOS devices. If you change the extension to .zip you will be able to unzip it and view the contents.