WCF is the foundation for creating services. It can be used to create web services, but WCF is rather agnostic regarding the main communication channel. Thus, WCF can also be used to implement (non-Web) TCP or UDP services, Windows services, and they can even be hosted in the process.
Conversely, web services can be implemented without WCF.
Ultimately, “WCF service” in and of itself simply means “a service that was implemented using the Windows Communication Foundation infrastructure.”
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