SSL is short for Secure Sockets Layer, which is a protocol for sending private documents on the internet. On our shared hosting plans our SSLs are server wide, so you can use it at no additional cost. However if you feel you need more protection you can use a 3rd party provider including Komodo or Geotrust. You can view this information at http://cfdynamics.com/ecommerce/ecommerce_addons.cfm.
If you are going to a secure site and you are wondering about the level of security, you can view the current SSL by clicking on the lock in the bottom right corner