At the present time a number of particles is known which corre spond to various quantum fields interacting with each other. However, of the many types of physical interactions existing in nature the only one, apart from gravitation, that has been studied in sufficient detail is the electromagnetic interaction. The theory of the latter interaction is the subject of quantum electrodynamics, to which the systematic exposition of this book is devoted.
Since the electromagnetic interaction is the fundamental one in the case of electrons and photons, quantum electrodynamics enables us to explain and to predict a wide range of phenomena related to the behavior of these particles.