What is a calorie and what do they mean?
A calorie is the amount of energy that is needed in order to heat 1 litre of water at 1-degree Celsius. A calorie is basically a unit of energy.
Calories in macronutrients are-
Carbohydrates have 4 calories per gram
Protein has 4 calories per gram
Fats have 9 calories per gram
Alcohol has 7 calories per gram
An example here would be-
If you had a food that contained 10 grams of carbohydrates then this would equal to 40 calories.
When your calories in match your calories out (when they are the same) then this means that you are keeping your calories/body at your maintenance level.
Example- Burning 2,000 calories and eating 2,000= Maintenance calories as you are maintaining the weight that you are currently at.
Maintenance calories will remain the same when calories out(what you burn) vs calories in(what you eat) are the same. In order to lose weight you would have to be in a deficit and in order to gain weight you would have to be in a surplus but if you wanted to stay the same then you would be at your maintenance.