BPMN 2.0 Process, Collaboration, Choreography and Conversation

Process

A Process describes a sequence or flow of Activities in an organization with the objective of carrying out work.
Process is depicted as a graph of Flow Elements, which are a set of Activities, Events, Gateways, and

Sequence Flows that define finite execution semantics.

Processes can be defined at any level from enterprise-wide Processes to Processes performed by a single person.
Low-level Processes can be grouped together to achieve a common business goal.

BPMN uses the term Process specifically to mean a set of flow elements
It uses the terms Collaboration and Choreography when modeling the interaction between Processes

Business Process modeling is used to communicate a wide variety of information to a wide variety of audiences.
BPMN is designed to cover many types of modeling and allows the creation of end-to-end Business Processes.
There are three basic types of BPMN Processes:
1. . Private Non-executable (internal) Business Processes
2. . Private Executable (internal) Business Processes
3. . Public Processes

The Collaboration package contains classes that are used for modeling Collaborations, which is a collection of Participants shown as Pools, their interactions as shown by Message Flows, and MAY include Processes within the Pools and/or Choreographies between the Pools
A Choreography is an extended type of Collaboration

A Collaboration usually contains two or more Pools
Pools represent the Participants in the Collaboration
The Message exchange between the Participants is shown by a Message Flow that connects two Pools (or the objects within the Pools)
The Messages associated with the Message Flows MAY also be shown
A Pool MAY be empty, a “black box,” or MAY show a Process within
Choreographies MAY be shown “in between” the Pools as they bisect the Message Flows between the Pools
All combinations of Pools, Processes,and a Choreography are allowed in a Collaboration.