Web service is a software service used to communicate between two devices on a network.
More specifically, a Web service is a software application with a standardized way of providing interoperability between disparate applications. It does so over HTTP using technologies such as XML, SOAP, WSDL, and UDDI. A Web service involves a service provider and a service requester (client). Because Web services feature language transparency, it doesn’t matter whether the underlying system that provides the service is written in Java while the client is written in Perl, Python or Ruby. For example, through Web services, a Windows server can interact with a Linux server or serve an application to computer desktops, laptops or smartphones and other mobile devices over the World Wide Web.