Application data makes up the core of the data storage on Xamarin platforms and Windows Runtime. This data is specific to your application. It lives and eventually dies with it, and in most cases it is not relevant or even accessible by other applications running on the same device or even by the user who is using the application (at least directly).
The application has unrestricted access to application data, or so-called isolated storage, without having to ask for permission from the user or add a declaration and can (in most cases) write, read, and query items in this storage according to the type of the application data location.
The installation directory is the innermost part of the accessible data storages and is the most intimate location for the application. Access to this location by the application is unrestricted but read-only. The access models on iOS, Android, and Windows Runtime vary greatly.