This an AMRAP, "As Many Rounds As Possible". You are free to take breaks whenever you want, even in the middle of an exercise. The idea is to go through this entire set of exercises as many times as you can during the set amount of time you give yourself (15 or 20 minutes). If the timer goes off and you are in the middle of a round, feel free to either finish off the round or just stop the workout if you are pressed for time.
Some music if you need:
Get into plank position with your hands placed shoulder-width apart. Lower your body bending your elbows and bringing your knee to touch your elbow. Bring your chest as close to the ground as possible. At the lowest point, push back up and reset back to starting position. Repeat with other knee.
Stand straight and place your hands on your hips. Inhale while taking a step forward with your right leg while keeping your back straight. As you land on the heel of your right foot, bring your left knee towards the ground while maintaining your center of gravity. Exhale while pushing off your right heel back to standing position. Repeat other side.
Lie face down. Raise your forehead slightly off the ground a few inches and extend your arms out in front. Raise your left hand, your right leg, and your head simultaneously. At the top, pause for 1 second. Release and go back to starting position. Repeat other side.
Lie flat on your back. Bring your hands behind your ears and raise your shoulders slightly off the ground. Bring your legs up, about 45 degrees off the ground. Twist your body and have your right elbow contact your left knee. Then twist and have your left elbow contact your right knee. Keep this movement slow and controlled. Inhale while starting the rotation, exhale while ending the rotation and completing the movement. Repeat.