WCF is a programming model that enables developers to build service solutions that are reliable and secure, and even transacted. It simplifies development of connected applications and offers something to developers that they have not seen in quite a while — a unified, simplified, and manageable distributed system development approach.
Windows Communication Foundation (WCF) is a framework for building service-oriented applications. Using WCF, you can send data as asynchronous messages from one service endpoint to another. A service endpoint can be part of a continuously available service hosted by IIS, or it can be a service hosted in an application.