List a physical, mental and emotional, and social benefit of physical activity. Physical: Weight reduction, or just maintenance.
Mental/Emotional: Stress reduction, because of the endorphins release.
Social: Make new friends.
When you practice a physical activity, you not only have the obvious physical benefits, but also some mental, emotional and social ones.
Physical activity is recommended to reduce weight, this is the most common and visible effect. However, it has many other benefits in your body, such us tension reduction, which helps in Hypertensive people, and cholesterol reduction. All the energy needed to move every muscle in your body and make your blood run through your vains, results in benefits to your heart, brain and heart.
Some mental and emotional benefits are related to the endorphins release that makes you feel happier and consequently reduces stress.
Regarding social benefits, it will depend in the activity you practice. Most of them you share with other people, so we can say physical activity helps you to make new friends or build a team with other players, if we talk about a team sport.