Apple - What does .ipa stand for?
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.
According to Apple, .ipa stands for "iOS App Store Package". Wait a minute, that makes no sense at all. It originally stood for:
iPhone Archive
Then, when iPhone OS became iOS, they made up this new translation for it to make its purpose more clear.
IPA stands for "iOS App Store Package", according to Apple them self - read the iOS Developer Library - section "Tools Workflow Guide for iOS->Distributing Apps".
Sending Your App to Testers
To send your app to testers:
If you don’t have access to the project that generates the app, obtain an iOS App Store Package (IPA) file for your app from the appropriate teammate. Otherwise, generate the IPA file yourself:
a. Open the project in Xcode.
b. Archive your app.
c. Generate an IPA file for your app.
Download the user testing provisioning profile for your app from the iOS Provisioning Portal to your file system. (You don’t have to install this profile in Xcode.)
Email the user testing provisioning profile and the IPA file to your testers.