An IPA (iOS App Store Package) is the native file format for iOS apps. Think of it as a .exe file for Windows or .apk for Android. Official IPAs are encrypted with Apple’s FairPlay DRM. However, cracked or decrypted IPAs (which are legal to own for backups in some jurisdictions) allow installation on older firmware.
: Specifically patched for iOS 12 users to fix crashing and login issues. YTLitePlus youtube ipa for ios 12