"SOAP is a protocol for exchanging XML-based messages over computer networks, normally using HTTP/HTTPS. SOAP forms the foundation layer of the web services protocol stack providing a basic messaging framework upon which abstract layers can be built."

Let's get a first look of SOAP's XML figure (courtesy of Sun Microsystems)
It is quite simple that SOAP is AKO XML message that the web service/client use to communicate each other.
On this step, I am just started to learn how to assemble data in to XML chunk. The next step is to write a client to request and decode that XML into readable information.