Aerobic exercise is fat burning exercise. As you do some activity using large muscles (legs, especially) that raises your heart rate but still allows you to breathe normally, your body will burn fat with the oxygen you’re breathing. However, your body will only burn blood-sugar at first, because it’s easily available. So, to get to the fat-burning stage, you have to exercise for at least 20 minutes, preferably 30 minutes or more. Walking and bicycling at a gentle pace are aerobic activities.
Anaerobic exercises are high-intensity exercises that get your muscles working hard, and you will have trouble breathing. The word “anaerobic” means “without air”, meaning that you will be breathing fast, but still not getting enough oxygen to properly fuel your muscles. This leads to muscle strengthening, but it also means that you’re burning blood-sugar only, not fat, and you end up with lactic acid that will make your muscles feel like they’re burning. Weight training and sprinting are anaerobic activities.
You can keep doing aerobic exercise longer than anaerobic exercise, and you’ll burn about equal amounts of calories overall doing either. Aerobic exercise burns those calories from fat during the exercise. Anaerobic exercise only burns blood-sugar, but burns a lot of fat later (the rest of the day) to replace the energy. Is it possible to combine the two, so that you can burn fat while exercising, and keep burning the rest of the day? Yes, with Interval Training.