What is WSDL2APEX and Use of WSDL2APEX in Salesforce
Apex Classes can be automatically generated from a WSDL document.
Use of WSDL2APEX:
Developers can be used to invoke the external Web service Using generated Apex Class.
Generate from WSDL2APEX is available in Sandbox or a Developer Edition.
Setup -> Develop -> Apex Classes ->
And hit the button called ‘Generate from WSDL’
To Know more about WDSL2APEX, Salesforce Developer