When you reach Leatherworking level 225 and Character Level 40 you will be eligible quest for one of three different Leatherworking paths: Dragonscale, Elemental, and Tribal Leather. Each has their pros/cons...i suggest you research those yourself. As a side note, you can still level past 225 without choosing a path and you will still have many non-specific leather items that you can craft. These branches just allow you to make a few, specialized armor pieces.