Windows Communication Foundation (WCF) was introduced with the release of .NET Framework 3.0. This release of the .NET framework was in essence Version 2.0 along with four additional components:
WCF is meant to provide a unified programming model to build, configure, and deploy services on distributed networks. It combines well-known technologies that have been around for some time, such as .NET remoting, Web Services Enhancements (WSE), MSMQ, ASMX, and message-oriented programming.
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The preceding diagram is provided courtesy of wcftutorial.net. If our introduction to WCF makes you curious about WCF and its technologies, this website does a great job of explaining it in detail.