The Van Allen belts are large regions encircling the Earth (some distance into space), containing energetic charged particles consisting of relativistic speed electrons and ions captured from the solar wind by the Earth's magnetic field. Such regions are termed radiation belts. The particles are potentially harmful to humans in space within the belt regions, but the belts are protective to the lowest Earth orbits and the Earth's surface, reducing cosmic rays as well as solar particles from extreme solar eruptions (e.g., the Carrington event). (I'm guessing it is the Earth's magnetic field which is protective for capturing particles rather than letting them through.) Other bodies with magnetic fields can have similar regions, termed their Van Allen belts.