Getting rid of (or lessening) a stomach flap

TDEE is the common abbreviation for Total Daily Energy Expenditure which is a metric to calculate the amount of calories your body needs to function in a day. This is quite similar to BMR; in fact, you need your BMR to calculate your TDEE; but your TDEE accounts for your average daily activity as well to give a figure truer to your specific situation. Basically, the TDEE calculation relies on categorizing your daily activity into one of the metrics' predetermined groupings:

Sedentary - desk job and little to no exercise
Lightly Active - light exercise/sports 1-3 days/wk
Moderately Active - moderate exercise/sports 3-5 days/wk
Very Active - hard exercise/sports 6-7 days/wk
Extremely Active - hard daily exercise/sports & physical job or training

Once you have determined where you fit in on the TDEE activity rate scale, this activity rate is used to weight your BMR giving you a more accurate assessment of how many calories you really need throughout the course of the day. Since BMR only accounts for your bodies basic functioning needs and not your daily activity, TDEE provides standard multipliers for accurately determining a TDEE. Those multipliers are as follows:

Sedentary - 1.2
Lightly Active - 1.375
Moderately Active - 1.55
Very Active - 1.725
Extremely Active - 1.9