Scoring your paper refers to pressing a crease or almost a cut into your paper by using a heavy hand and usually a sharp pencil. You might score your paper when you are pressing too hard with a harder pencil like some of the H series pencils such as 3H or 5H. You can score your paper with anything even if it is more blunt. What happens is that you might hold the pencil really tightly and push really hard into the paper to get a line just right, to transfer an image with tracing paper or to decisively draw over something. This causes the pencil to dig into the paper and make a line that is pressed into the surface of the paper. You can score paper that is below the paper that you are currently drawing on in your pad of paper. These scored lines from a drawing that was drawn on top of the next piece of paper can press so deeply into the paper that you can never cover them since the are deeper into the paper than your pen or pencil will go. Typically when drawn over they leave a white line made by the deep groove in the paper.