Despite what the majority of society believes, a calorie is not an object in food. A calorie is a unit of measurement. Technically called a kilocalorie, one calorie is the amount of energy that is required to raise the temperature of one kilogram of water one degree Celsius.
This means that the number of calories on a nutrition label is related to the amount of energy provided. That being said, different foods provide different amounts of energy. Calories come with a negative connotation because of the side effects. However, they are required for survival. Basal metabolic rate (BMR), also known as resting metabolic rate (RMR), is the amount of energy through calories required just to lie on the couch for the day (to run cardiovascular, respiratory, endocrine, digestive, and all the body's systems).
Calories are the fuel to your body. Just as you use fuel to give your car energy, you must give yourself fuel (food) to give yourself energy.
Video from LSGScience (YouTube)