This action is used for specifying actions to be run in parallel.  This may be desirable for running large action processes. To specify the processes for parallel execution, double click on the action box to see a down arrow with a 'Drop activity here' message. The only actions/activities that can be dropped into this box are:

Invoke Workflow or Invoke Workflow Static

Parallel Task Properties:

DisplayName : This property is of type String and contains the name of the action box.

CompletionCondition:  This property is of type Boolean and specifies the completion condition of the Parallel task using a Visual Basic Boolean expression.