Web services are software components that expose their functionality to the network. To exploit that functionality, Web service consumers must be able to bind to a service and invoke its operations via its interface. To support this, we have two protocols that are the fundamental building blocks on which all else in the Web services arena is predicated: SOAP and WSDL. SOAP is the protocol via which Web services communicate, while WSDL is the technology that enables services to publish their interfaces to the network. In this chapter we cover both SOAP and WSDL in some depth and show how they can be used together with rudimentary tool support to form the basis of Web services-based applications.