Aerobic (under 75% of max heart rate) will burn fat. Anaerobic will promote cardiovascular health but you don't want to stay anaerobic for an extended period of time. You'll use up all the glucose in your liver and be hit with the dreaded bonk.

You can replenish glucose with simple carbs like sugar. You also need to stay hydrated and keep your sodium and electrolytes up. Gatoraid does a good job. I prefer Cytomax as it tastes better. If sodium levels drops, you'll start shedding potasium. That can lead to death.

After heavy exercise don't ever gulp down large amounts of water. That will dilute sodium which will result in low potasium levels.