SOAP webservice mobile application

Question

Dear people,

I'm working on a project which contains a simple .HTML file with Ajax and J query and a C# SOAP Web-service. The whole project will be made for an I phone and I pad application but can't find any solution on how to fix that kind of problem since I'm a beginner.

What does the client(.HTML) says to the Service?
Well, that isn't complicated. It sends a .XML file to the service. The service reads it, goes to the database and retrieves information and sends it back to the client. Then the looks of the application will be determined by the values the SOAP message contains and sends a second message and contains the values for an Query. Then the same procedure and done is the loading of the page.

Why do i need help?
I'm an learning type of guy and I'm fascinated by the way webpages get there info of an webservice, except I don't know how? I have a file which contains some XmlHttpRequest but how does it works? What does it sends? How do i know the service gets it and post "Successful" down in <p>tag</p>? So much question i know, but it's important for me.

Hoping for some helpful answers,

Sincerely,
Jordi Roer.