Definition - What does Web Service mean?
A Web service, in the context of .NET, is a component that resides on a Web server and provides information and services to other network applications using standard Web protocols such as HTTP and Simple Object Access Protocol (SOAP).
.NET Web services provide asynchronous communications for XML applications that operate over a .NET communications framework. They exist so that users on the Internet can use applications that are not dependent on their local operating system or hardware and are generally browser-based.
Techopedia explains Web Service
The main advantage of a Web service is that its consumers can use the service without knowing about the details of its implementation, such as the hardware platform, programming language, object model, etc. Web service provides a loose coupling between heterogeneous systems with the help of XML messages, provide interoperability.
Web services are designed to provide the messaging infrastructure necessary for communication across platforms using industry standards. Web services also use asynchronous communication to address the latency issue that arises due to requests from remote locations across the Internet. This allows the execution of background tasks for the client (such as responding to user interactions) until the actual completion of the Web service request.
ASP.NET provides a framework that can be used to build Web services easily by focusing on the application logic rather than on the hardware necessary for writing infrastructure code for communication protocol or message transport. Web services created in ASP.NET can use features of the .NET framework such as caching, authentication and state management.
Web service uses the ".asmx" extension with the @Web service directive (at the top of file) as per the ASP.NET application model. It can be a stand-alone application or a subcomponent of a larger Web application.