On many webhosts there is an option called "Anonymous FTP". That service allows anyone access to upload or download files. JerseyWebHostng does not allow anonymous FTP. The public_ftp folder is therefore unused for anonymous FTP purposes.
You can rename or use the folder as you otherwise see fit.
Anonymous FTP is an insecure service that can open your site to illegal usage. You can create FTP users for anyone needing access to your account.
