A BOSU ball is a versatile fitness tool that looks like a half-sphere attached to a flat base. It can be used for various exercises, helping to improve balance, strength, and stability. The dome side can be used for workouts like push-ups or squats, while the flat side can serve as a stable platform for other exercises. Using a BOSU ball engages your core muscles more than traditional workouts, making it a popular choice for athletes and fitness enthusiasts. It's also great for rehabilitation, as it allows for low-impact exercises that can help strengthen muscles without putting too much strain on joints.