The book is devoted to the most promising type of thermonuclear installations used to create and study high-temperature plasma. It was at such facilities that record results were achieved in heating and retaining hot plasma. The book is based on lectures given by the author in 1967-1968. the French Atomic Center in Saclay . The first three lectures are devoted to the main questions of the theory: the geometry of magnetic fields, equilibrium conditions and physical processes on which the stability of the plasma depends. The fourth lecture presents the results of experimental work performed in the laboratory led by the author at the Institute of Atomic Energy named after I. In. Chicken. In presenting the questions of the theory, the author sought to avoid the use of a complex mathematical apparatus and focused on clarifying the physical mechanism of the main processes. The book can be useful for scientists - physicists and engineers interested in plasma physics, as well as for undergraduate students in physical and engineering-physical specialties.