R.tools

This application shows you how to group your resources in your Android project and provide alternative resources for specific device configurations.

You should always externalize application resources such as images and strings from your code, so that you can maintain them independently. You should also provide alternative resources for specific device configurations, by grouping them in specially-named resource directories. At runtime, Android uses the appropriate resource based on the current configuration. For example, you might want to provide a different UI layout depending on the screen size or different strings depending on the language setting.

For more information, see http://developer.android.com/guide/topics/resources/providing-resources.html