Name 

Description 

Deferred Event (UML 2.0) 

A deferred event is like an internal transition that handles the event and places it in an internal queue until it is used or discarded.
A deferred event may be thought of as an internal transition that handles the event and places it in an internal queue until it is used or discarded. You can add a deferred event to a state or activity element. 

History Element (State Machine Diagrams) 

The Shallow History and Deep History elements are placed on regions of the states.
There may be none or one Deep History, and none or one Shallow History elements in each region. If there is only one history element in a region, it may be switched from the Deep to Shallow type by changing its kind property.
Please refer to UML 2.0 Specification for more information about these elements. 

State 

A state models a situation during which some (usually implicit) invariant condition holds. The invariant may represent a static situation such as an object waiting for some external event to occur. However, it can also model dynamic conditions such as the process of performing some activity (for example, the model element under consideration enters the state when the activity commences and leaves it as soon as the activity is completed). 

Transition 

A single transition comes out of each state or activity, connecting it to the next state or activity.
A transition takes operation from one state to another and represents the response to a particular event. You can connect states with transitions and create internal transitions within states. 

UML 2.0 State Machine Diagram Definition 

States are the basic units of the state machines. In UML 2.0 states can have substates.
Execution of the diagram begins with the Initial node and finishes with Final or Terminate node or nodes. Please refer to UML 2.0 Specification for more information about these elements. 

UML 2.0 State Machine Diagram Elements 

The table below lists the elements of UML 2.0 State Machine diagrams that are available using the Tool Palette.
UML 2.0 State Machine diagram elements