Hi Sanwar , You can refer this link :https://www.c-sharpcorner.com/UploadFile/govind77/introduction-to-service-oriented-architecture/

Service-oriented architecture (SOA) is an architecture pattern that is based on designing services as primary component to implement and perform business and non-business functionality. WCF supports three message exchange patterns i.e., request-reply, one-way (also called datagram), and duplex (also called callback). Please refer https://msdn.microsoft.com/en-us/library/ff395349.aspx for more details on WCF messages