The path, relative to the build's workspace, to the generated .ipa (iOS), .app.zip (MacOS), or .apk (Android) file.
You can include build variables here like ${BUILD_NUMBER} and they'll be expanded at build time.
e.g. "MyApp/build/Beta-iphoneos/MyApp-Beta-${BUILD_NUMBER}.ipa if your use ${BUILD_NUMBER} as technical version number (CFBundleShortVersionString).