The binding element describes the message format and the protocol details for specific operations ans messages defined by a particular portType. In a WSDL 1.1 you can have many bindings for a given portType.

The name attribute of the binding element is used for defining a unique name among all the bindings that can be defined within the WSDL 1.1 document.

The type attribute of the binding element is used for referencing the portType that it binds.

The following is an example of the binding element in a WSDL 1.1 file. 

<wsdl:binding name = "WSDemoSoapBinding" type = "impl:WSDemo">
    <wsdlsoap:binding style = "document" transport = "http://schemas.xmlsoap.org/soap/http"/>
    <wsdl:operation name = "helloWorld">
        <wsdlsoap:operation soapAction = ""/>
        <wsdl:input name = "helloWorldRequest">
            <wsdlsoap:body use = "literal"/>
        </wsdl:input>
        <wsdl:output name = "helloWorldResponse">
            <wsdlsoap:body use = "literal"/>
        </wsdl:output>
    </wsdl:operation>
</wsdl:binding>