As well as uploading individual files, you can upload an entire folder of files in a single step. Once complete, a new Google Drive folder will be created that has the name of the original folder you uploaded. Any subfolders will show as sub-folders, and all documents will remain in the same sub-folder as in the original.
To upload an entire folder of documents into Google Drive:
From the Google Drive home page, click on the New button
Choose Folder Upload
Choose the folder you wish to add to Google Drive
Click on Upload
The Upload pane will show the progress of the folder upload - click on Cancel at any time if you want to cancel the current upload.