Web service is basicaly a class which contains methods and its methods is to be called by methods on other machines on another network via one of common data formats and protocols like XML and HTTP. In .NET this method calls are commonly implemented through the SOAP(Simple OBJECT Access Protocol) which is an XML based protocol and DESCRIBE how to mark up requests and RESPONSES so that they can be transferred via protocols such as HTTP. Using SOAP data is transmit in a standardized XML based format.

Web service is simply a software component PLACED on one machine that machine can be accessed by an application or software component on another machine over a network. The machine where Web service RESIDES is referred to as a remote machine. The application that accesses the Web service sends a method call over a network to the remote machine, which processes the call and returns a response over the network to the application.