This form is called either from the Documents form or the Add Documents form when you choose a zip file (or similar) to add to the documents repository.
Extract Files
You can either extract the files and add them individually or add the zip file directly.
Apply to all remaining files
This option is only available if more than one zip file has been chosen. Switch it on to apply the chosen option to the rest of the files. Otherwise this form will be displayed for each zip file.