Official Description: The Support Library is a static library that you can add to your Android application in order to use APIs that are either not available for older platform versions or utility APIs that aren't a part of the framework APIs. Compatible on devices running API 14 or later.

CommonsWare’s Notes

This library contains a few classes that may be of use if you are creating custom views. The most popular one is ViewDragHelper, for helping you manage drag-and-drop sorts of interactions in a custom ViewGroup.

ViewDragHelper originated with the Android Support Library, and so many of the articles and blog posts that are written about it will refer to the edition of the class. Much of that material will still be accurate — you just need to switch to the androidx edition of the class.