Shepherd moons are small natural satellites that orbit within the rings of a planet, helping to maintain the structure of those rings. They exert gravitational forces that can create gaps and waves in the ring material, influencing the distribution of particles. A well-known example of a shepherd moon is Prometheus, which orbits Saturn. It plays a crucial role in shaping the planet's F ring by pushing particles outward and creating a distinct edge. This interaction between shepherd moons and ring systems is essential for understanding the dynamics of planetary rings.