The book examines a wide range of issues related to the study of the nature of various rare effects that are incomprehensible to observers, generally defined by the term “anomalous phenomena,” which also received the common name “unidentified flying objects - UFOs.” The historical aspect of the study of these phenomena is considered, and a critical analysis of various approaches to the study of their nature is carried out. Specific physical models of the development of various types of anomalous phenomena, both natural and man-made, are given, as well as an assessment of the philosophical and sociological aspects of the problem. The book is intended for readers interested in the history and results of scientific research on UFOs.