An is the result of taking those split components and merging them back into a single, "universal" APK file. This allows you to install the app using Android's native system installer without needing extra tools like "XAPK Installer". How to Convert XAPK to APK Online
The most reliable way to "repack" and install these files is using an installer that handles the extraction and placement automatically. online convert xapk to apk repack