The Document Page displays the Documents in the Document Library but you can also embed a custom document library showing only a subset of the documents on your website as show in the video below.
Any media or document in the Media Library is available in the Document Library. But you can also use External Links to add external documents such as Google Docs to the Document Library.
The following video shows how to embed a Document Library on a page or post and how to add external files such as Google Docs to the document library.
See the following video for more information on External Documents.