The basics of the theory of linear and nonlinear electromagnetic processes in passive and active media. The interaction of the electromagnetic field with the electron flux, dielectric, magnetic and plasma media, the issues of frequency conversion, amplification and generation. are considered. The theory of waveguides, including complex configurations and resonators. The construction of the book is deductive, based on Maxwell's equations and wave equations of electrodynamics . The reduction of equations to a four-dimensional form (electrodynamics of moving media) makes it possible to determine a number of dependencies between the characteristics of the electromagnetic field and the medium .. The application summarizes the applied mathematical apparatus and basic information from quantum mechanics.