The main difference between web service and WCF service is that WCF is a superior replacement for the technologies of web service from Microsoft. With the web service, the user needs to know how to receive and send SOAP (Simple Object Access Protocol) messages. SOAP uses XML and HTTP for data description and data transport. It is a relatively straight forward approach, as all you need to know for web service is how to navigate SOAP.
WCF (Windows Communication Foundation) It is used for generating service-oriented applications. It assists in sending information from one service endpoint to another service endpoint as messages. The messages sent can be single words, characters, or sophisticated binary information. There is also higher convenience and flexibility in using WCF.