Some people dread it, some people love it, but no matter where you stand, cardiovascular health is critical to overall health. Without going into too much detail, your heart pumps oxygen and nutrient blood through your body, allowing your nervous system, organs, muscles and basically everything else in your body function properly. In terms of fitness, good cardiovascular strength allows you to perform exercise for longer periods of time. Many people do cardio training as a means to burn fat and trim down. It's often associated with time on the treadmill, spin bike, stair master, etc. Steady-state cardio, training at a constant speed or resistance for a prolonged period of time, can help burn fat.
However high intensity interval training and high intensity circuit or interval work will not only help build up cardiovascular strength and endurance, but help burn fat faster. For those that dread hitting the treadmill, jogging, etc. Try adding workout finishers like this circuit to the end of your normal weight training routine.
Between the burpees and the pike push-ups, this circuit is a shoulder burner. If your shoulder tire out in the later rounds, simply swap the pike push-ups for a pike hold. Hold for 15-20 seconds and rest.