shepherdMoon

Given a predicate that represents a relationship or action between entities, generate a one-sentence description explaining its meaning.  
# Instructions
Focus on describing the relationship, not the entities themselves. 
# Response Format
Begin the description with \' Indicates...\'

Predicate: shepherdMoon

Indicates a relationship where a small moon orbits near a planetary ring and gravitationally shapes, confines, or maintains the structure of that ring.