The property 'Actor ' ,different between Line and Human task

When I click one Line .There is a property name Actor and I can assign to this Line .
Then I click a human task in the Line ,There is a property name Actor too ,And I can assign a diff Actor to it .
I understand that actor means who do this task , and I can understand the Actor of the human task
But what the means of the actor of a LNE???

Hi.
The actor in the Lane is an actor that is the same for all the human tasks in this Lane.
If you set the actor in the Lane, for each human task you can choose “use the actor define in lane”. Like this you don’t need to define a new actor each time your create a task.