'Jumping' is the colloquial term for transiting across any of the wormhole-like connections between the Jump Points that comprise the ancient and presumably artificial Jump Network. Jump based travel is the foundation of all known interstellar economies, as it is the only known practical method to overcome the enormous distances involved in a timely and affordable fashion.
The rapidity of Jump based transit is achieved by moving through shortcuts that fold the structure of the universe, rather than following a path along more 'normal' space-time. Jump Drives are devices capable of rendering these shortcuts exploitable for movement. As no extant species has demonstrated the technological capability to create folds connecting such distant points in space, let alone create a fold with sufficient persistance and transport capacitance for material transit, Jumping can occur only at existing Jump Points.