SSL (Secure Socket Layer) is a protocol that transmits information over the Internet in an encrypted form for security purposes. POP/SMTP over SSL encrypts all data exchanged between your mail client and the FatCow mail server with a digital security certificate to protect your password and messages.
You can find an example for configuring your email client with SSL in the Fatcow Hosting FAQ. The Ports used are always the same so you can adapt the settings for your own email.
Con Doesn't secure the email itself
This has nothing to do with securing the email itself, only securing its transmission on one part of its journey. Anyone will still be able to read it if intercepted while being transmitted to the destination server, or while sitting on the destination server.