The main concepts of the new theory of processes with the participation of excess electrons in polar liquids are considered. The theory takes into account that (1) polar liquids are electrostatically inhomogeneous (local potentials on molecules are different) and (2) a molecule can accept an electron for a short time to produce an anion in an unstable state with a certain energy and lifetime. A discrete model of a substance consisting of molecules with constant dipole moments is used. Excess electrons in a liquid are described by energy distribution density, and the behavior of electrons, by quantum mechanics equations. The experimental data on the photoionization of water and aqueous solutions of salts and the low threshold energy of photons (∼6.5 eV) at which solvated electrons appear in water are explained. The absorption spectra of water with excess electrons at the first and subsequent time moments after their photogeneration are reproduced theoretically. The dependence of the photoemission of solvated electrons from potassium-ammonia solutions on the energy of photons is interpreted. The continuous spectrum of spontaneous radiation of solvated electrons in liquid ammonia and water is calculated. The optical absorption spectra of solvated electrons in such polar liquids as water and ammonia are reproduced.