Android.app or Android.graphics Library? Or classes storage? Who “on the fingers” can explain?

Answer 1, Authority 100%

android.app and android.graphics are packages (Packages). If on the fingers, then the packages are a named set of classes (and possibly packets). Packages group classes with similar functionality.

Answer 2

It is correct to call this package (in Java terminology) with a set of classes. At the same time, other packages may be inside the package.

Answer 3

Android.app This package containing high-level classes intended for describing the general model android applications. There are four main components for applications for android use of which is regulated by the functionality of the application being developed: Activity, Service (located in the Android pack) and BroadcastReceiver, ContentProvider (located in the Android .Content package). The package also defines classes describing Dialogs, Notifications and Action Bar, which can also be component of applications.

Android.graphics is a package containing classes providing low-level graphic tools.