Secure Socket Layer (SSL) is the standard way to implement secure Web sites. By encrypting the traffic between the server and the client, which is what SSL does, that content is protected from a third party listening to the traffic going past.
All of the traffic exchanged is encrypted once the SSL session has been set up. This means that even the URLs being requested are encrypted.
The exact mechanism by which this encryption is accomplished is discussed extensively in the SSL specification, which you can read at http://wp.netscape.com/eng/ssl3. For a more user-friendly discussion of SSL, we recommend looking through the mod_ssl manual, which you can find at http://httpd.apache.org/docs/2.2/ssl. This document not only discusses the specific details of setting up mod_ssl but also covers the general theory behind SSL and contains pictures illustrating the concepts.
You also may wish to see the TLS 1.0 (RFC 2246) specification, which provides what might be thought of as the next generation of SSL. You can read the full specification at http://www.ietf.org/rfc/rfc2246.txt, or you can find a more friendly explanation at http://en.wikipedia.org/wiki/Transport_Layer_Security.
In this chapter, we talk about some of the common things that you might want to do with your secure server, including installing it.
You want to install SSL on your Apache server.
The solutions to this problem fall into several categories, depending on how you installed Apache ...