A Choreography Model is similar to a business process model which consists of flows of activities, events, and gateways. Instead of having normal activities, a choreography model shows choreography activities which represent interactions between the participating roles.
The Conversation Model is a simplified view of collaboration model. There are only three types of elements in a Conversation Model - pools, communication elements and the links between them.
http://blog.maxconsilium.com/2013/09/bpmn-20-models-part-2.html
GAB C