Usually refers to activities that increase your heart rate.

Aerobic exercise mostly intended to expend calories and burn fat, and of course, strengthen the heart.

Any form of exercise that strengthens the lungâ€(tm)s ability to provide oxygen to the blood and the heartâ€(tm)s ability to pump that blood to the various cells in the body. Cardio workouts also promotes cardio respiratory endurance which allows the heart and lungs to sustain activity for an extended length of time.