This chapter describes the essential concepts and building blocks of 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; and understand some related topics, such as in-proc hosting and reliability. Even if you are already familiar with the basic concepts of WCF, I recommend you give this chapter at least a cursory reading, not only to ensure 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.