The book is based on a course of lectures given to students of the 3rd and 4th courses of the Faculty of Physics of Moscow State University, specializing in theoretical physics . The first part of the book contains an exposition of the basic ideas of the theory of gauge fields, the construction of gauge-invariant Lagrangians and a description of the spectra of linear excitations, including over a nontrivial basic state. The second part is devoted to the construction and interpretation of solutions, the existence of which is entirely due to the nonlinearity of the field equations, solitons, "Euclidean bubbles", instantons and sphalerons .. The material presented can be studied in parallel with the study of quantum mechanics, and then quantum field theory. In this regard, the book should be useful to both researchers and graduate students, as well as senior university students . I will add from myself that as a student, I got acquainted with the basics of the theory of gauge fields . from this book.