This is where you used to be able to make a "document". Be it a word processing, spreadsheet or Presentation document.
Now it is just that. A document. (No not a Word .doc!)
Now that they have file storage and a greater ability to upload files it now acts as a "Drive". You can even download "Drive" and it acts as a folder on your computer. Anything you put in your "Drive" shows up on line as a Google... Doc.