Your heart rate, or pulse, is the number of times your heart beats per minute.
Normal heart rate varies from person to person and can be altered by physical exercise, sleep, anxiety, stress, illness, and ingestion of drugs.

In the app you can find additional metrics, such as:

Resting heart rate (rhr)
Resting heart rate is the rate at which your heart beats when you are at rest. For a healthy person the resting heart rate is normally between 60 beats per minute and 100 beats per minute. Changes in resting heart rate can be an indication of changes in your fitness level. Active people often have a lower resting heart rate because their heart muscle is in better condition.

Heart rate recovery (hrr)
Heart rate recovery is the difference in heart rate at peak exercise and the heart rate measured after a one minute recovery period. The health band measures heart rate recovery when you are exercising with your heart rate being at least 80% of your maximum heart rate for a minimum of ten minutes. The measurement starts when the health band registers change from a high-intensity activity to a low-intensity activity. To obtain an estimate of health rate recovery, sit down immediately after stopping your activity and then rest for at least 2 minutes to let your heart rate recover.