The book is devoted to the presentation of the elementary thermal theory of combustion. The main attention is paid to the thermal side of the phenomenon with a significant schematization of the representations of chemical kinetics. Examples of combustion of a homogeneous combustible mixture, carbon (coke) and unmixed gases reveal the meaning and features of exothermic reactions: possible stationary levels of the process, critical phenomena of ignition and extinction, thermal flame propagation, process stability, etc. The influence of various parameters is considered: blast rate, composition of the mixture, caloric content and its initial temperature, etc.