This addon created a side bar to list all documents in your googledoc application. You can view file properties, rename file, mark/unmark file to be starred and hidden, move file to trashbin, export and download file directly, create new documents directly. This version will not support folder. It will be added in next one.
For google oauth, you can learn more from http://code.google.com/apis/accounts/docs/OAuth.html
For client login , you can learn more from http://code.google.com/apis/accounts/docs/AuthForInstalledApps.html