Web Services or XML Web Services are application programming interfaces (API’s) or software applications that are designed to support interoperable machine-to-machine interaction over a network. Web services enable quick integration of applications across multiple platforms, systems and even across businesses. Web services allow different applications from different sources to communicate with each other easily because all communication is made in XML open standard format.
Windows Services are background processes that usually have no direct interaction with the user interface. These services are long-running executable programs that run in the background, ideal for use on a servers whenever there is a needed long-running functionality.
Recently Appdec's team has started using the latest Microsoft service-oriented framework called WCF (Windows Communication Foundation) for building connected systems using the Microsoft .NET Framework.