In regard to the calorie question:
Calories are units of energy. Remember that.
The basic theory is that the body requires a specific number of calories to keep itself running properly and stay healthy. Basic operations, such as cell repair and breathing, require you to use calories for them.
If one weighs 200 lbs, she would need to eat 2,000-2,200 cals a day to maintain that weight. If she wants to lose weight, and is pushing for a safe 2 lbs weight loss per week, then the caloric intake would be reduced by 800-1,000 calories each day. It is commonly taught, that in general, the body needs a daily intake of 1.200 calories just to keep up with daily needs, from the cellular level to basic activities of daily living (walking around house/work, brushing teeth, etc).
However, if you are very active and/or exercise every day, and yet to stick to eating just 1,200 cals, then you're stealing the calories needed for basic living and health to use to fuel your extra activities. This is why you'll see added calories to your suggested/allowable intake. You want to eat enough cals to feed your body
and fuel your activity/exercise. Not either/or.
Does that explanation help?