An app that has been modified to include new features by expert developers is known as modded apk or mod apk. It is a modified version of an official app. The term modded apk or mod apk is used to describe an app that has been modified by professional developers. The APK file is the file that contains the app's extension. The APK is the file that contains the app's modification. It is a modified version of an official app that has been modified. Just like an APK file, a mod APK is also known as an app with extra functions. For example, the paid app for which you're searching may be downloaded for free here. According to my humble understanding, if an app has been edited and redesigned with some unique features that are not available in the official version of that app and those features are also demanded by Android users, then it is better to have an mod version.