Calories are a unit of measurement used to quantify the amount of energy that food provides when consumed. In simple terms, a calorie is the energy your body gets from food, which it uses to perform daily functions like breathing, moving, and even digesting food.
When we talk about the calories in food, we're usually referring to kilocalories (kcal), which indicate how much energy you can obtain from a particular food or drink. The body uses calories from the macronutrients (carbohydrates, fats, and protein) to fuel its functions.