Colleen Morrow goes into conversations in the context of Service Broker:
Like real-life conversations, Service Broker conversations are a reliable-bidirectional stream of messages exchanged between two participating services. A Service Broker conversation can be short-lived, a simple exchange of 2 messages, or it can span days, weeks, even years. There are two key elements of a Service Broker conversation that are important to note, however. The first is that messages are guaranteed to be delivered in order, and only once. Service Broker uses sequencing and acknowledgement mechanisms to ensure this. The second key is that conversations are persistent. Persistent across network interruptions. Across server restarts. In fact, conversations persist until they are explicitly ended.
In the world of Service Broker, you’ll sometimes see the term “conversation” used. Sometimes it’s “dialog”. Sometimes it’s even “dialog conversation”. Although “conversation” and “dialog” are distinct concepts in the greater world of messaging services, in the context of Service Broker they are interchangeable.
We’re getting close to seeing Service Broker in action here, so stay tuned.