A web service is a program that can be invoked over the Internet, providing information or functionality. It can deliver content in many ways, including static webpages coded in HTML; through file exchanges such as downloads and uploads; text documents; image files; and more. Web services can be interoperable across different programming languages and operating systems. They are often defined using the Web services description language (WSDL), which is a self-describing, common XML grammar that describes the functionality and interfaces of a Web service. And, they can be published and discovered through the Universal Description, Discovery, and Integration (UDDI).
A Web service implementation is designed to be composable, allowing a simple web service application to be built out of component web services. This allows the implementation to be more agile and adaptable to change. Examples of a web service could include a latittude/longitude to state code converter or a vacation booking system composed out of a flight search, hotel reservation and rental car company booking services.
microsoft web services are a set of services that enable developers to integrate Web applications and Web services into their applications. These include the Web Service API, which enables you to call a web service and provides role-based authorization.
Windows Server 2012 R2 and later provides the Microsoft Web Services (WWS) API, which is a new, modern SOAP stack that offers best-in-class performance and memory usage. This API makes it easy for C++ developers to create and use web services.