WSDL : Java Glossary

WSDL is an XML (extensible Markup Language) format for describing network services as a set of endpoints operating on messages containing either document-oriented or procedure-oriented information. The operations and messages are described abstractly and then bound to a concrete network protocol and message format to define an endpoint. Related concrete endpoints are combined into abstract endpoints (services). WSDL is extensible to allow description of endpoints and their messages regardless of what message formats or network protocols are used to communicate, however, the only bindings described in this document describe how to use WSDL in conjunction with SOAP (Simple Object Access Protocol) 1.1, HTTP (Hypertext Transfer Protocol) GET/POST and MIME (Multipurpose Internet Mail Extensions).
~ W3 organisation

Huh? Why do these academics create tools for programmers then go to such lengths write such bullshit as documentation? Because they are more interested in impressing fellow academics than producing useful tools. WSDL is much like XSD (XML Scheme Definition), a schema for describing SOAP messages. You can see a sample WSDL schema for the response from the allposters.com SOAP service at http://webservice.allposters.com/ProductInformationService.asmx?WSDL