Calorie is a scientific unit for energy, historically defined as the energy needed to heat water by 1 degree Celsius, and is related to the combustion process requiring fuel, oxygen, and temperature.

“calorie actually is very often people think then immediately of nutrition and and foods and these kind of things but it's actually just a unit is actually just a unit a scientific unit actually for for knowing how much energy is needed to heat water from from from 14 to 15 degrees for example a certain amount of that and then how many how much calories is needed so we could even use gasoline for this but it basically comes back to the fire triangle you need something to combust you need oxygen and you need temperature”