Merge pull request #4172 from kiwix/Fixes#4146

Added a section in the README file to showcase the two variants of our application.

README.md

@@ -67,6 +67,56 @@ necessary to comply with the Play Store policies and ensure a smooth
 user experience.  We recommend using the official version of the app
 available on our website to access the complete set of features.
 
+## App variants
+
+Starting from version `3.12.0`, Kiwix is available in two variants which are slightly different:
+
+- [Google Play version](https://android.kiwix.org/) using application id `org.kiwix.kiwixmobile`
+- [Full version](https://download.kiwix.org/release/kiwix-android/) using application id `org.kiwix.kiwixmobile.standalone`
+
+### What are the difference between the two variants?
+
+While the core functionalities remain the same, the primary difference
+lies in the ability to access ZIM files located outside the (Kiwix)
+reserved app directories.
+
+The Google Play version has a limitation when it comes to scan and
+open ZIM files from anywhere in your device storage, as mentioned in
+the [Important Notes](#important-notes).
+
+In contrast, the full version of the application can load (and scan
+for) ZIM files directly from other storage locations via the file
+picker... without requiring them to be copied or moved to the reserved
+app directories.
+
+### Why two variants?
+
+To avoid confusion between the Google Play version and the full
+version, we introduced dedicated application ids (one for each
+variant). Using the same application id for both versions caused
+conflicts with the Google Play Store, as it treated them as the same
+app. This resulted in scenarios where Google Play would prompt updates
+for the full version. If users updated through the Play Store, they
+would lose advanced file management capabilities (such as scanning
+storage or directly opening ZIM files using the file picker).
+
+This separation ensures clarity for users and prevents undesirable
+behavior.
+
+### How to move content between two variants?
+
+You can move the bookmarks by exporting and reimporting them. The
+feature is available in the "Settings".
+
+Regarding ZIM files, you should move them to - or from - the reserved
+app directories `Android/media/org.kiwix.kiwixmobile/` or
+`Android/data/org.kiwix.kiwixmobile/`. This might have to be done for
+both internal storage and SD card.
+
+Kiwix can detect automatically all ZIM files available in your
+storage. You just need to swipe down in the local "Library" screen and
+it will scan your storage and recognize all your ZIM files.
+
 ## Android permissions needed
 
 Kiwix requires the following permissions to fully work: