In this chapter we present a detailed discussion of the particle-antiparticle mixing in the SM and perform the classification of various types of CP violation. We will discuss the determination of the CKM parameters in tree-level decays and also the determination of the so-called unitarity triangle from particle-antipartcle mixing both from Band K meson systems and tree-level decays in question. In this context we will present various methods for the determination of the angles in this triangle from certain leading decays. The considered decays are subject to only small contributions from NP so that the CKM parameters can be extracted without knowledge of what happens beyond the SM. This is useful as then the results of tree-level determinations of CKM parameterscan be used to find SM predictions forparticle-antiparticle mixing observables considered already in this chapter and for rare processes considered in the next two chapters. Both particle-antiparticle mixing and rare processes are subject to potential NP contributions and could help us to identify NP through the pattern of deviations of the data for themfrom SM predictions.