Jets are found in a wide range of accreting young stars, from brown dwarfs to massive protostars, but their launch region(s) and their role in angular momentum extraction are still debated. Many observational constraints exist on jet properties, including jet widths, kinematics along and across the jet, possible rotation signatures, ejection/accretion ratio, depletion and molecular counterparts. This contribution compares popular models, in particular disk winds, with these constraints and with MHD numerical simulations, highlighting a few open issues.