QCD factorization is the only theoretical instrument to make a bridge between Perturbative QCD (PQCD) and physics of hadrons at high energies. There are known two conventional forms of factorization: Collinear and kT factorization. We present a new and most general form of factorization: Basic Factorization and trace its step-by-step reduction first to kT Factorization and then to Collinear Factorization. In any form of factorization, perturbative calculations are complemented by non-perturbative inputs which are usually introduced without any theoretical grounds. We obtain theoretical restriction on the inputs, suggest a Resonance Model for them and compare this model to the models available in the literature.
