Every body system benefits from exercise. To begin with, exercise is great for the heart, lungs, and cardiovascular system in general. The more we exercise, the more blood the heart pumps and the stronger and more efficient it becomes. At the same time, the lungs get better at oxygenating the blood that is important for every organ/body system. From the muscle/skeletal system standpoint, exercise can help improve strength, flexibility, power, endurance and bone density, thus helping to live a more active lifestyle.
Exercise can also help improve mental wellness.