What Is a Calorie?

A calory is the amount of ener that it takes to raise a cubic something of water by one degree. You burn, i don't know, a piece of paper underneath a little cube of water, and the water gets slightly warmer. So in physics, historically, the small calory is defined as the amount of energy that is needed to increase the temperature of one gram of water by 1 degree celsius. That's at sea level.