Pion Structure at High and Low Energies in Chiral Quark Models

Low and high energy properties of the pion are reviewed in the framework of chiral quark models. Particular emphasis is put on the simplest version of the SU(2) NJL model as prototype. The role of gauge invariance in this kind of calculations is stressed. The results are used as initial conditions for perturbative QCD evolution equations. At leading order the quark model scale is ${\mu }_0\sim 320\mathrm{M}\mathrm{e}\mathrm{V}$ as determined from the pion distribution functions and the pion distribution amplitudes.