This webinar will present the physical basis of cloud electrification and lightning formation, showing the need for total lightning information in real time and how the GLM Ray Mapper of GOES-16/17 satellites meets these needs. The principles of lightning detection in soil and space will also be addressed, as well as the detection methods and definitions of the variables observed by the GLM. Some products derived from GLM observations and some of the many application areas are shown, such as the immediate forecast of convection and severe weather, warnings of imminent risks of cloud-to-ground discharges, aviation, atmospheric chemistry studies, quantitative estimation of precipitation, tropical cyclones, forest fires, numerical forecast of weather and climate and climate and global studies.