This is a considerably revised English translation of the Russian original of 1993. It gives a rather complete survey of the astrophysics of planetary nebulae, including theory and observations. The book covers various subjects ranging from various aspects of emission lines, ionization equilibrium, electron temperature, the ultraviolet and the continuous spectra, the infrared radiation and radio emission all the way to distances, dimensions, dynamics and, finally, the origin of planetary nebulae. It addresses students as well as professional and amateur astronomers.