Beam often refers to the radiation pattern of an antenna. Mostly it refers to the radiation pattern of satellite antennas. Depending on the size of the illuminated area of the earth's surface, a distinction is made between a global beam (large area) and a spot beam (small area).
In the case of a spot beam, the radiation lobe has only a small aperture angle, so that only a small footprint is created on the earth's surface. The size of the illuminated earth surface also depends on the satellite concept. Near- Earth orbiting satellites, LEO satellites, typically operate with a smaller footprint than off-Earth satellites such as the MEO satell ites or the GEO satellites.
The shape of the beam can be circular or elliptical, which depends on the elevation angle of the satellite.