The review, which is methodological in nature, discusses the most common mechanisms of stimulated radiation of electron beams such as single-particle and collective Cherenkov effects, undulator and synchrotron radiation, the anomalous Doppler effect, and Thomson and Raman scattering and radiation. The relation between the mechanisms of spontaneous radiation of an individual electron and stimulated radiation in electron beams is made clear, the basic principles of linear electrodynamics of radiative beam instabilities are stated, and the principal mechanisms of their nonlinear stabilization are investigated. The discussion of widely different stimulated processes in electron beams is carried out from a unified point of view with use of a simple mathematical apparatus and such generally accepted physical laws as the conservation laws and Newton's laws. Therefore the review, which is intended for specialists in the fields of plasma electrodynamics and high-frequency electronics, is written also for persons familiar with only the fundamentals of physics taught in a general university course.