Metabolism?

what is a fast metabolism? slow?Metabolism?
Having a "fast" metabolism means that you're burning calories efficiently all the time, whether you're resting or training. When you have a slow metabolism, your diet doesn't work as well and even a well-designed training program is rendered less effective. Slow metabolism syndrome is why it's possible for a person eating very few calories and "aerobicizing their brains out" to see little or no results.
Someone that gains weight easy has slow metabolism even if they're eating normal amount of calories. Someone who no matter how much food they consume they never gain weight. That's a person with fast metabolism.
it's how fast or slow your body burns up calories etc.
a fast metabolism burns calories fast/slow burns slow. the older a person gets the slower their metabolism gets.