This chapter introduces the fundamental concepts of Quantum Chromodynamics (QCD) phenomenology and its application to high-energy scattering experiments. It begins by deriving the QED cross-section for electron-muon scattering and the Mott cross-section, which provides the template for hadronic processes. The discussion then extends to elastic electron-proton scattering, introducing the concept of form factors (GE and GM) to account for the composite nature of the proton, culminating in the Rosenbluth formula. The chapter proceeds to analyze inelastic scattering and deep inelastic scattering (DIS), where the hadronic final state is described by structure functions and the Bjorken x variable. This naturally leads to the introduction of the naive parton model and the subsequent treatment of QCD evolution via the DGLAP equations to account for gluon radiation and the \(Q^2\) dependence of parton distribution functions (PDFs). Finally, the text briefly explores other key processes like hadron production in electron-positron annihilation and the Drell-Yan process, which provide complementary tests of the strong interaction theory.