The book explores the current state of laser dynamics and provides reference data and basic experimental facts for old- and new-generation lasers. The most frequently used mathematical models are presented. The author discusses the reasons for the spontaneous occurrence of pulsation of the intensity of radiation of solid-state lasers and the influence of the non-stationary nature of laser elements on lasing characteristics. Special emphasis is placed on the problems of the low-frequency dynamics of multimode lasers. This book is aimed at experts in the fields of quantum electronics and laser physics.