A chain stopper is a crucial device used to secure the anchor chain, taking the load off the windlass and ensuring safe anchoring operations. It is essential to always use a chain stopper when setting or riding on the anchor, as it holds the chain in place and prevents undue strain on the windlass. Additionally, a chain stopper is vital for breaking the anchor free and preventing accidental free fall of the anchor while underway, enhancing overall safety and reliability of the anchoring system.