Satellite Communications can be defined as the use of artificial satellites to establish communication links between various points on the Earth's surface, i.e., a telecommunication system encompassing at least one communication satellite. The combination of the New Space era with the exploitation of low-altitude nodes led to a broadening in the family of communications from the sky: Non-Terrestrial Networks (NTN), which include the use of airborne and spaceborne nodes to establish communication links between various points on the Earth's surface. The International Telecommunication Union Radiocommunication (ITU-R) sector follows a well-established procedure to define requirements, request submissions by external organizations, and evaluate radio interface technologies for the definition of International Mobile Telecommunications-2020 (IMT-2020). Such principles and procedures are reported in ITU-R Resolution 65, and they are applicable to both the terrestrial and NTN components of IMT-2020.