This volume provides an introduction to the astrophysics of jets from young stars. The first half is devoted to general observational constraints, covering the outflow phenomenon in young stars, the identification of magneto-centrifugal processes as the main jet driving mechanism and the magnetic interaction between star and its accretion disc. The second half is devoted to theoretical knowledge of magneto-hydrodynamic processes pertinent to the jet launching mechanism in young stars. This comprises a general introduction to magneto-hydrodynamics, a description of the role of MHD processes in Standard Accretion Discs and the physics of steady state MHD outflows, from the basic concepts and equations to modern self-similar solutions. Further coverage details the various classes of steady magnetic wind models currently discussed in the context of protostellar jets.