ABC is the three building blocks of WCF and they are known as
A – Address (Where) : Address tells us where to find the services, like url
B – Bindings (How) : Bindings tells us how to find the services or using which protocols finds the services (SOAP, HTTP, TCP etc.) . Read more about Different Types Of Binding In WCF
.C – Contacts (What) : Contracts are an agreement between the consumer and the service providers that explains what parameters the service expects and what return values it gives.