What are Web Services ? Give an example ?

Web services allow access to software through standard web protocols such as HTTP and SMTP. They enable software to interact with a wider range of clients. Web services can be consumed by any application that understands how to parse an XML. XML is the key technology used in web services.
Microsoft .net web services support three protocols HTTP GET, HTTP POST and SOAP (Simple Object Access Protocol).
For the clients to interact with the web services there must be a description of the method calls or interface that the web service supports. This web service description document is found in the XML schema called as WSDL (Web services description language).