Recent experiments seem to be ready to answer the question whether QCD be the correct theory of strong interactions at all scales, or just an effective high-energy line of a yet undiscovered theory. With the upgraded Large Hadron Collider, a proton-proton collision will reach the Center of Mass (CoM) energy of 14 TeV per colliding pair. Perturbative QCD will then be tested with the highest precision. In this realm, the present book begins reviewing QCD with the aim to focus on the Drell-Yan process and the experiments conceived to validate it. In doing this the approach will be exclusively perturbative. Non perturbative techniques, such as lattice QCD, QCD sum rules, or concepts like the MIT bag model will not be discussed.