An activity diagram is a behavioral graph that shows a system's behavior. An activity diagram shows the control flow from a starting point to a finishing point, highlighting the various decision paths while performing the activity. An activity diagram can depict both sequential and concurrent processing of activities. They are commonly used in business and process modeling to describe the dynamic aspects of a system. A flowchart is very similar to an activity diagram. Activity Diagrams depict the flow of control in a system and refer to the steps involved in the execution of a use case. Using activity diagrams, we model sequential and concurrent activities.