Cardio is a short term for cardiovascular. Cardiovascular is a term used for the circulatory system consisting of the heart and blood vessels. If you didn't know heart is a muscle and needs to be exercised. If you don't exercised for 20 minutes or longer you have the possibility to get a heart disease. You could get a heart disease because the less you work your heart gets weaker. It doesn't really matter what kind of exercise or activity you do but you need to be moving your whole body.