The Web Services Description Language (WSDL) provides an XML format for describing the services associated with the web service application. According to the W3C's WSDL specification, "WSDL is an XML format for describing network services as a set of endpoints operating on messages containing either document-oriented or procedure-oriented information." WSDL is a format for defining the services that exchange information through SOAP messages.
A WSDL document is primarily a set of definitions. The definitions within the document specify information on the data being transmitted and the operations associated with that data, as well as other data related to the service and the service location.
WSDL is not confined to SOAP but is also used with other web service communication protocols. In some cases, WSDL is used directly with HTTP to simplify the design and restrict the actions to more fundamental GET and POST-style operations at the heart of HTTP.