The term `New-born` refers to a new vampire, i.e. someone who has just been changed. They are stronger than regular vampires because they still have human blood in their system, but they also have a harder time controlling themselves since the bloodlust is so new to them. In the South, they were said to have wars, so to speak, over territory by using new-born vampire armies. This is what happened to Jasper, and is why he has so many scars on his back.