There are two ways to create a webservice, top-down and bottom-up. In top-down approach, you start with a XSD, WSDL and generate the necessary stub classes using some web service code generation tool like wsdl2java etc... In bottom-up approch you start with a Java method, and generate the WSDL from it. Either way you need WSDL and webservice engine to deploy the service.
You can develop webservice using axis2, metro etc . If you are new to webservice, start with some basics and understand the terminology first : go through WebServicesFaq