IDEF3 is concerned with modeling the processes of a business or its systems. The primary IDEF3 diagram is the IDEF3 Process Flow diagram. The primary symbol representing a business process is called a Unit of Behavior (UOB).
IDEF3 process flow diagrams
You generally start with a scenario diagram, which describes the overall process of a part of the business or a system. The Units of Behavior on this IDEF3 Scenario diagram are IDEF3 Decomposition Diagrams that show further detail of the process flow.
IDEF3 object state modeling
IDEF3 is also concerned with modeling the state behavior of business objects, through the use of the Object State Transition Network (OSTN) diagram.