Star Jumps: These are similar to Jumping Jacks. Stand with knees slightly bent and feet shoulder-width apart on a flat surface. Your arms should be slightly bent at your sides. Bend your knees to get into a squat position and jump vertically as high as you can. Extend your legs and arms fully out to your sides at the same time in midair to form a star shape with your body. Your arms should point upward at a 45-degree angle away from your head. Bring your arms and legs inward near your body as you begin to descend from the jump. Land softly on the ground with your knees bent. Squat and push off vertically again to perform a second star jump. This exercise can be done repeatedly. By pulling your limbs inward on the descent, you prepare yourself for successive jumps. If Star Jumps are too difficult, you can modify them and do Jumping Jacks instead which include a hop, rather than jumping and landing in the same position.
Here is a great photo to help you better understand the movement.
This image is from Extreme Fitness Martial Arts website. When you’re ready to take your fitness to another level, Extreme Fitness Martial Arts suggests doing 4 sets of 25 Star Jumps with only 30 to 60 seconds rest between sets!