Can Web services be used in other communication platforms besides the Web?

Yes, they can. Web services are described by WSDL, which is used to describe a service using XML, not necessarily one that is used over the Web. In order to understand this last statement, you need to ask the question: What is necessary for operation over the "Web"? The answer, in one word, is "HTTP." The Web implicitly means transporting information over HTTP as the communication protocol. In fact, as you probably know, one of the most popular means of using Web services is over JMS, as an alternative to SOAP over HTTP.

 So the question arises - why are Web services called Web services? Some believe that Web services really means a "web of services" rather than services that assume the Web. We can play around with definitions and words till the cows come home, but the key concept to grasp is that that Web services is a group of well-defined services, and don't automatically assume HTTP. Perhaps WSDL is the misleading term - it should just be an SDL (service definition language).