What is SSL?
Secure Sockets Layer, SSL is a protocol developed by Netscape for transmitting private documents via the Internet. SSL works by using a public key to encrypt data that's transferred over the SSL connection.

All modern web browsers, Netscape, MSInternet Explorer, Opera, Lynx, and others have built-in in support for SSL. Web sites use the protocol to obtain confidential user information, such as credit card numbers, between the client browser and the server, by encrypting the information between the two.

By convention, URLs that require an SSL connection start with https: instead of http:, and the communication takes place over TCP/IP port 443 (by default) rather than port 80 for non-secure communication