A UML Activity Diagram is a general purpose flowchart with a few extras. It can be used to detail a business process, or to help define complex iteration and selection in a use case description. It includes:

	Active states - oblongs with rounded corners which describe what is done.
	Transitions - which show the order in which the active states occur and represent a thread of activity.
	Conditions - (in square brackets) which qualify the transitions.
	Decisions - (nodes in the transitions) which cause the thread to select one of multiple paths.
	Swimlanes - (vertical lines the length of the diagram) which allow activities to be assigned to objects.
	Synch States - horizontal or vertical solid lines which split or merge threads (transitions)