The jab is a mostly under publicized punch as it normally lacks the power of other punches, but it is the one you hear being shouted by trainers / instructors in boxing, kick boxing and MT all the time. It is a great little punch, which is used to set up your opponent for the big punch. it provides protection via the counter, It is used by some fighters quite effectively to unsettle or force an opponent to loose concentration. A good jab will put your opponent of guard and ideally lift your opponents head or make them drop thier gaurd. One big mistake fighters make is to pull the jabbing hand back, jerking the hand etc (tellegraphing) before throwing the punch this only leads to an experienced fighter getting ready to counter. To throw a good jab you should ensure the elbow comes up to your shoulder level and fire out forwards (difficult to explain and easier to show.) For added power a push forward and a slight rotation of the shoulder can be implemented. Anyway hope this is of some use to the new fighter?