From http://www.w3schools.com (Copyright Refsnes Data)

You Have Learned SOAP, Now What?

SOAP Summary

This tutorial has taught you how to use SOAP to exchange information between applications over HTTP.

You have learned about the different elements and attributes in a SOAP message.

You have also learned how use SOAP as a protocol for accessing a web service.

Now You Know SOAP, What's Next?

The next step is to learn about WSDL and Web Services.

WSDL

WSDL is an XML-based language for describing Web services and how to access them.

WSDL describes a web service, along with the message format and protocol details for the web service.

If you want to learn more about WSDL, please visit our WSDL tutorial.

Web Services

Web services can convert your applications into web-applications.

By using XML,  messages can be sent between applications.

If you want to learn more about web services, please visit our Web Services tutorial.

From http://www.w3schools.com (Copyright Refsnes Data)