You just noticed your little bundle of joy is throwing a ball at a shoulder height to a person standing at a small distance from him by making full use of his arm strength and even by raising it perfectly to throw.
What you need to know:
Congrats, it is a sign of strong muscle strength. When your child plays throw ball, frisbee, football, etc. in his daily play he will be to improve his muscle strength. Keep a check on his nutrition and ensure to have at least one hour of outdoor playing session. It will help him build his stamina and muscles. Your participation for his growth will only build his confidence to indulge in such activities.