The Dumbbell Fly is a strength training exercise primarily targeting the chest muscles, specifically the pectoralis major. It involves lying on a flat bench while holding a dumbbell in each hand, arms extended above the chest. The movement consists of lowering the dumbbells out to the sides in a wide arc, then bringing them back together above the chest. This exercise helps improve muscle definition and strength in the upper body. It can be performed with variations, such as using an incline or decline bench, to target different areas of the chest. Proper form is essential to avoid injury and maximize effectiveness.