This chapter describes the essential concepts and building blocks of Windows Communication Foundation (WCF) and its architecture enabling you to build simple services. You will learn the basic terms regarding addresses, bindings, contracts, and endpoints; see how to host a service; learn how to write a client; understand related topics, such as in-proc hosting, reliability, and transport sessions; and see how to utilize WCF in Visual Studio 2010. Even if you are already familiar with the basic concepts of WCF, I recommend that you give this chapter at least a cursory reading, not only to ensure that you have a solid foundation, but also because some of the helper classes and terms introduced here will be used and extended throughout the book.