We briefly review recent achievements in experimental and theoretical studies of the spin dynamics of electrons and trions under optical pulse-train excitation. The microscopic origin of spin coherence generation, control and detection by means of light is uncovered. The specific features of spin-Faraday, Kerr, and ellipticity signals are analyzed. We show that these effects provide complementary information about spin dynamics. The equilibrium spin dynamics probed by the spin noise spectroscopy is also discussed.