Those are the paths traced by your eyes. It does say “and often the mouse,” but it’s describing reading, and the common habit of following along with the mouse cursor as you read. IF you are the kind of person who does this, it puts the mouse cursor in the right place for you when you’re ready to click. This does not help, A) people who don’t do that, B) people who are using a keyboard or assistive device, or C) people using a mobile/touch device.