Caption: : This is a key concept when programming Greenfoot. This is that the various Actors and the World - using references - can communicate or talk to each other. They cannot communicate without references.
Caption: : This is to go in the prepare section in the World. This is adding the Counter object - manually - into the world. This can be done automatically by dragging the counter where you want it and pressing "Save the World".
Caption: : If you could please pay attention to the purple box. The reason the word "counter" is placed in the brackets for when the Turtle is being created is that when that is done, a reference for the counter to the turtle is being created. Now the turtle will know and recognize the counter, therefore it can tell the counter to update a score if needed, when the parameter is updated on to its own class area for coding and programming.