Immediate mode provides a way of modeling without building an operator stack. Using this mode is equivalent to freezing the Modeling construction region of the selected objects after every operation.
Immediate mode is especially useful when moving points or adding and extruding polygon components. The stack does not fill up with a large number of operators, and therefore, scenes are smaller and quicker to update.
Whenever you apply an operator in immediate mode, its property editor opens with OK and Cancel buttons. Make all the changes
you want before clicking OK to confirm that you are satisfied with the results. If you are editing multiple objects (for example,
if you select several objects and choose Deform 
Twist), the same values are applied to all objects.
Be very careful when using immediate mode: when it freezes the modeling stack after each operation, it removes any previously applied operators.
In particular, you will lose any animation applied to operators' parameters, such as the amplitude of a deformation. For more information, see Freezing the Operator Stack.
If you want to be able to replay commands from the history, don't use immediate mode. When you get a primitive or apply an operator in immediate mode, the corresponding property editor opens with OK and Cancel buttons. If you change a parameter value while the property editor is open, no SetValue command is logged.
As a result, you will get different results when you play back commands from the history.
