Basically, a *web service* is an application with which other applications can communicate over via a network, often using XML to encapsulate data and context, and HTTP as the transport layer. There are several ways (protocols) we can expose our web services to the rest of the world, from a the minimalistic approach of the "RESTafarians", to using XML-RPC, to SOAP and all its accompanying specifications (UDDI, WSDL, WS-Security, WS-Context, etc.)