Net Calories? Could someone explain?

I am new to the idea of calories, and am certainly new to the idea of net calories.  Essentially aren't they the BMR- what you've eaten?  This number might increase if you have exercised, right?

I've read that for weight loss you should aim for -500 a day, which comes out to -3,500 a week.  Supposing you manage to do that, about how much weight would the average person lose a week?

At what point is your net calorie number no longer considered healthy?

On a side note, what do *you* strive for?

Net calories is the difference between the total you burned in a day (not just exercise) and the total you ate. If Net is negative, then you have a deficit, if Net is positive, you have a surplus. If Net is zero, you are eating at maintenance.

BMR is basal metabolic rate, or what you would burn in a coma. I suggest eating at least that amount.  CC does not directly tell you your BMR (it uses it to figure out how much you burn, but doesn't state anywhere what it is). There are plenty of websites that will calculate it for you.

For many people, -500 cal net (or 500 cal deficit) per day is best - that would be 1lb lost per week. If you are over 200lb, you might be ok with a deficit of 1000 calories (2lb/week loss), although you would still want to make sure you were eating enough (again, I suggest eating at least your BMR).