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

DocumentFile helps you use document Uri values, such as those that you get from ACTION_OPEN_DOCUMENT, ACTION_CREATE_DOCUMENT, and ACTION_OPEN_DOCUMENT_TREE. DocumentFile makes it easy for you to get at the “display name”, size, MIME type, and other document metadata. For document trees, you can use DocumentFile to list the children of a tree, create new children, etc.