Android app contain source, resource like layouts, drawable contents, menu, String, icons, and build setting to compile and run the android application. Android app are written in java.
Android sdk tool compile your source, along with any data and resource file to an archive file with .apk extension called android package. An apk contains all the necessary files of your app that is required to install the apk on Android powered devices.
Once an apk installed on a device, each android app lives in its own security sandbox:
There are 2 ways to share data/file of one application with other: