Theoretical Aspects of Rare Kaon Decays

Most of the analytic approaches which are used at present to understand Kaon decays, get their inspiration from QCD in the limit of a large number of colours $N_c$. After a general overview, we illustrate this with a recent application to the evaluation of the process $K_L\text{ra}{\mu }^{+}{\mu }^{-}$ in the Standard Model.