Microsoft Windows Communication Foundation (WCF), alongside Windows Workflow Foundation (WF) and Windows Presentation Foundation (WPF), has become part of the primary framework for building the next wave of business applications for the Microsoft Windows operating system. WCF provides the underpinning technology driving distributed solutions based on the Microsoft platform; with it, you can build powerful service-oriented systems designed to address connected services and applications. WCF is also an integral technology for building and accessing services running in the cloud under Windows Azure.
You can use WCF to create new services as well as augment and interoperate with many existing services created by using other technologies. When designing distributed applications in the past, you frequently had to choose a specific technology, such as Web services, COM+, Microsoft Message Queue, or .NET Framework Remoting. That choice often had a fundamental impact on the architecture of your solutions. In contrast, WCF provides a consistent model for implementing scalable and extensible systems that employ a variety of technologies with which you can design and architect your solutions without being restricted by a specific connectivity mechanism.
In short, if you are building professional, service-oriented solutions for Windows, you need to learn about WCF.