This lecture covers the description and classification of radiation sources, including fast electron sources, heavy charged particle sources, electromagnetic radiation sources, and neutron sources. It explains the energy range of ionizing radiation, the concept of radiation hardness, and the processes of beta decay, internal conversion, and Auger electrons. The lecture also delves into alpha decay, spontaneous fission, and the production of beta emitters by neutron irradiation. Additionally, it discusses the characteristics of gamma rays, X-rays, and photoneutrons, as well as the mechanisms of neutron production through various reactions.