When you look at a nutrition label on food packaging, you'll often find detailed information about the number of calories per serving 

Calories are units of energy provided by food.

The number of calories in a food item can vary depending on its macronutrient content -carbohydrates, proteins, and fats

general calorie values for each macronutrient  – Carbohydrates: 4 calories per gram – Proteins: 4 calories per gram – Fats: 9 calories per gram – Alcohol: 7 calories per gram

Foods can also contain calories from other sources such as fiber and certain types of sugar alcohols, but these are not typically listed separately on nutrition labels 

Total Calories: This represents the total number of calories in one serving of the food item

Remember, the total calories listed on the label represent the sum of the calories from fat, carbohydrates, protein, and alcohol (if applicable).  

It's essential to pay attention to portion sizes and servings per container