- A - Address (Where?)
This is the network address of your service saying where to find it. WCF support several address types/protocols. E.g. if you are creating a regular SOAP web service you would use an HTTP or HTTPS address. The type of the address depends directly on the binding type (see next definition).
- B - Binding (How?)
Binding defines how clients can communicate with our service. It specifies the transport protocol that should be used (HTTP, TCP, ...), web service protocol, encoding, security settins etc.
- C - Contract (What?)
Contract defines what functionality your service exposes. This is simply the interface that your WCF service implements.
Simple as ABC, isn't it? :)