[en] Physical foundations of γ-ray astronomy are briefly outlined. A survey is given of various physical mechanisms of the production of discrete and continuous γ spectra. The spectra of this radiation are changed during its passage through cosmic space and due to the interaction with interstellar and intergalactic matter; various mechanisms of such an interaction are described. According to the dominant interaction mechanisms in various energy regions, different types of γ-ray detectors are used (scintillation counters, spark chambers, nuclear emulsions etc.). The role of the terrestrial atmosphere as an absorber of γ radiation is discussed, and the design of γ-ray telescopes is outlined. Finally, the five essential problems of γ-ray astronomy are mentioned, and a brief survey of the first observational results of this new branch of astronomy is given. (author)