Official Description: The Resources Library is a static library that you can add to your Android application in order to use resource APIs that backport the latest APIs to older versions of the platform. Compatible on devices running API 14 or later.

CommonsWare’s Notes

Mostly, this artifact provides AppCompatResources, which contains a series of static methods (e.g., getColorStateList(), getDrawable()) that let you get resources the same way that AppCompatActivity does, for maximum compatibility.