A fitness tracker is a wearable device designed to monitor and record health-related metrics such as physical activity, heart rate, and sleep patterns. Utilizing built-in sensors like accelerometers and optical heart rate monitors, it provides real-time data on daily steps, calories burned, and exercise intensity. These devices typically sync with smartphone applications, allowing users to visualize their progress over time, set personal goals, and receive personalized insights to improve their overall well-being and athletic performance.