Aerobic means requiring oxygen or happening in the presence of oxygen.

In biology, aerobic describes processes that need oxygen to work. When you breathe hard during a jog, your muscles are doing aerobic respiration, using oxygen to convert food into energy. Bacteria that need oxygen to survive are called aerobic bacteria. The opposite is anaerobic, meaning without oxygen.

In exercise, aerobic activities are ones that make you breathe harder for an extended period, getting oxygen flowing through your body. Swimming, running, cycling, and dancing are all aerobic exercises. They strengthen your heart and lungs because these organs have to work to deliver oxygen to your moving muscles. You might take an aerobics class where you do rhythmic exercises set to music, all designed to keep your heart rate up and your breathing steady.

When something is aerobic, oxygen is the key ingredient. Your body's cells are like tiny factories, and during aerobic activity, oxygen is what helps those factories run at full speed. That's why you breathe faster when you exercise: your body is demanding more oxygen to power all that movement.