What is the difference between a watch and a warning?

A watch means atmospheric conditions favor severe weather forming; it's a heads-up to pay attention and have a plan ready. A warning means severe weather is actually occurring or is about to occur in a specific area right now — act immediately and move to shelter. Watches cover a larger area and longer timeframe; warnings are smaller, more urgent, and issued when the threat is real. Confusing the two is common and dangerous, so if you hear either one, immediately move toward your shelter location.