A Chest Strap HR Monitor is a fitness device that measures your heart rate. It looks like a belt that you wear around your chest. This belt has small sensors that read your heartbeat. These readings are then sent to your smartphone, smartwatch, or fitness app. The "HR" in the name stands for Heart Rate. Monitoring your heart rate during workouts helps you understand how hard your body is working. It shows if you’re training too hard, not hard enough, or just right. For example, if your goal is weight loss, you can stay in the "fat burn" heart rate zone. If you're training for a marathon, you might want to be in a "cardio" or "peak" zone.