Question about Photics book?

Devils

Alright this may sound dumb but in his book there are words highlighted in grey (i.e. game.X-Target-self.Position.X) what do these mean? Is the game.target where my information or images would go in?

retired_38652959dd1b99f014fb6a5e65a56927

The highlight signifies an attribute. I use the highlight color to emphasize that attributes should not be typed manually.