Introduction -- Flare Stars in a Quiescent State: General Characteristics of Flare Stars -- Photospheres -- Chromospheres and Transition Regions -- Coronae and Stellar Winds -- Heating Mechanisms for Stellar Atmospheres -- Flares: General Description of Stellar Flares -- Temporal Characteristics of Flares -- Flare Energy -- Dynamics and Radiation Mechanisms of Flares -- Models of Stellar Flares…