"One Arm Dumbbell Row" is a video demonstrating a unilateral exercise using a dumbbell to target the muscles of the upper back, including the latissimus dorsi, rhomboids, and trapezius. To perform this exercise, you typically place one knee and hand on a bench for support while holding a dumbbell in the other hand. With your back straight and core engaged, you pull the dumbbell upwards towards your hip, keeping your elbow close to your body and squeezing your shoulder blades together at the top of the movement. The video emphasizes proper form, technique, variations, and the benefits of incorporating one arm dumbbell rows into a workout routine to improve back strength, posture, and overall upper body development.