Cardio is any form of exercise with the goal of raising your heart-rate, as you move at more intense rate, your muscles require more blood and oxygen and therefore your heart works harder in order to fulfil that task.
Cardio has many benefits, but the most important is that your heart become more healthy!
There are also many additional benefits to cardio including: Weight loss, lower blood pressure, healthier cognitive abilites, aiding the endurance and oxygen capacity while doing Resistance training, and more to count.
There are 2 forms of cardio, each with similar but different outcomes; High-intensity cardio and steady-state cardio.
Watch this video to learn about the details of cardio and learn more about the 2 different forms of cardio