The purpose of this movement is to develop full body power and strength. The movement will work almost every muscle in your body with a focus on the shoulders.
Begin with a dumbbell on either side of your body. Your feet should be at shoulder width. Bend over and grab the dumbbells, but make sure to bend through your knees like a squat. Do not bend at the waist. Grasp each of the dumbbells and explosively pull the dumbbells from the floor to shoulder height. Then tuck your elbows underneath the dumbbells and catch them on your shoulders. Next, using your legs and shoulder muscles, drive the dumbbells overhead and lock out your arms. Carefully, lower the weights in the same manner, then repeat until your set is done.
This movement works a lot of muscles and can be difficult to master. Start with light weights and slowly move up once you get the hang of it. This can also be a very good cardio workout if done for higher reps, or it can be used to build total body mass with heavier weights.