The fundamental symmetries in the neutral kaon system—a pedagogical choice

During recent years experiments with neutral kaons have yielded remarkably sensitive results which are pertinent to such fundamental phenomena as {\cal C}{\cal P}{\cal T} invariance (protecting causality), time-reversal invariance violation, coherence of wave functions and entanglement of kaons in pair states. We describe the phenomenological developments and the theoretical conclusions drawn from the experimental material. An outlook for future experimentation is indicated.