What is Dynamic Modelling

 As you know that computer systems are built from the objects which respond to events.

External events arrive at boundary of system; you understand the concept of events. 

For illustration, whenever you click with your mouse on desktop or canvas area some action is triggered.

In dynamic modelling you observe "a process of describing how an individual object responds to the events, either the internal events triggered by other objects or the external events triggered by the outside world".