Creating and Accessing Web Services (Visual C#)
Web services enable applications to communicate in a loosely coupled environment by using predefined message exchanges built around standard protocols such as HTTP, XML, XSD, SOAP, and WSDL. Because the protocols and specifications are public and not platform-specific, Web services can be used to enable applications to communicate whether they reside on the same computer or not, even if they reside on different computing platforms or devices.
You do not have to understand each specification in detail to build or consume Web services. The .NET Framework classes and Visual Studio wizards help you build or interact with Web services by using a familiar object-oriented programming model.
For information, see Windows Communication Foundation.
The Web Services Developer Center on MSDN Online has additional articles and resources.