Suppose you have to make edit to the Drupal theme template.
But your client only gave you Drupal dashboard access, and no FTP access nor webhost access.
One such free third party program that I like is extplorer at extplorer.
It is PHP which will work on the server because Drupal runs on a PHP server.
You will now be able to edit your Drupal templates by download a copy of the file, making the change, and uploading it back up to the server.
How are you going to edit the template files on the server file system?
Well, one way is to have temporarily install a web file manager on the server.