When anonymous ftp is turned on in your account, anonymous ftp users have access to your /public_ftp folder.

To set things up for anonymous ftp access, log into your cPanel and click on "Setup anonymous FTP access". The first checkbox allows anonymous ftp users to download files from your /public_ftp folder. The second checkbox allows anonymous ftp users to upload to your /public_ftp/incoming folder.
No anonymous ftp users can view or download the contents of  the /public_ftp/incoming folder.

To connect with an ftp program as an anonymous ftp user, you need to use ftp@yourdomain.com as the username. Leave the password field blank. The hostname is ftp.yourdomain.com. Use port 21.