SSL stands for secure sockets layer. It is a security protocol to enable Web sites to pass sensitive information securely in an encrypted format. It is based on the RSA Data Security's public-key cryptography.
You can recognize Web pages that use SSL because the URL says "https://" and the Web browser will show some type of lock or other icon to denote that the connection is secure.
Do not submit sensitive data such as credit card numbers, identification codes, or other confidential information unless the Web site is secured using SSL.