An activity diagram is a flowchart that shows the steps that a system takes. It describes how a system works. It shows how control moves from where it starts to where it ends. This shows all the different ways the activity could go while it is being done. Like other UML use case diagrams, the Activity Diagram is made up of a flowchart that shows what a system does. Use cases and business processes can be described and explained with the help of activity diagrams. It is also used to keep track of how system operations are put into place.