Grive is still considered experimental. It just downloads all the files in your google drive
into the current directory. After you make some changes to the local files, run grive and
it will upload your changes back to your google drive. New files created in local or google
drive will be uploaded or downloaded respectively. Deleted files will also be "removed".
Currently Grive will NOT destroy any of your files: it will only rename local files to
start with a dot, or put it in the google drive trash. You can always recover them.