By analyzing the real space non-equilibrium dynamics of polymers, we elucidate the physics of driven translocation and propose its dynamical scaling scenario analogous to that in the surface growth phenomena. We provide a detailed account of the previously proposed tension-propagation formulation and extend it to cover the broader parameter space relevant to real experiments. In addition to a near-equilibrium regime, we identify three distinct non-equilibrium regimes reflecting the steady-state property of a dragged polymer with finite extensibility. Finite-size effects are also pointed out. These elements are shown to be crucial for the appropriate comparison with experiments and simulations.