To survive your body burns calories. Even if you spend the entire day doing absolutely no physical activity your body still requires calories to fulfill the processes that are required to maintain life, this number is known as your Base Metabolic Rate. When you add exercise or an active job into the mix you burn more calories. Total Daily Expenditure is the estimated number of total calories you burn each day. This calorie calculator is designed to show you both of those numbers.
These numbers are helpful if you are attempting to lose weight. To lose weight you need to burn more calories than you consume. If you have an idea of how many calories you burn you can adjust your calorie consumption, activity level or a combination of the two to achieve your goals. Keep in mind that a daily deficit of 500 calories is roughly what is required to lose one pound a week. Attempting to lose more than two pounds per week, which would require a daily deficit of 1000 calories, is generally considered to be safe but more than that is going beyond what I would recommend.
Remember the numbers from this calorie calculator are just estimates, the body is a complex machine and there are a lot of variables when it comes to losing weight.
If you have a certain goal that you are trying to achieve it may be beneficial to check out the goal weight calculator.
ALWAYS consult your physician before beginning any diet or exercise program.