Why are atlas Prometheus and Pandora called Sheppard moons?

Atlas, Prometheus, and Pandora are called "shepherd moons" because they help maintain the structure of Saturn's rings by exerting gravitational forces that influence the ring particles' orbits. As these moons orbit the planet, their gravity creates gaps and keeps the ring particles confined within narrow boundaries, preventing them from spreading out. This interaction results in distinct features, such as the well-defined edges of the rings and the formation of ringlets. Their role is crucial for the dynamic stability of the ring system.