XML Web Services provide a simple technique for accessing a method on an object that is running on a local or remote computer.  Web Services can be accessed by an application written in any language and running on any operating system.  They utilize HTTP as the underlying transport, which allows function requests to pass through corporate firewalls (as they move through port 80).  In ASP.NET we can write a Web Service as simple as a normal business object and the only difference is that the functions are preceded with a special <WebMethod ()>attribute that makes them as Web Services.  Typical implementation of Web Services might include shipment tracking, credit card verification, searching for airfare rates, Weather forecasting, etc.