The fundamental unit of energy in the metric system is the joule which is the energy required each second to push an ampere of current through an ohm of resistance. Heat is the energy of molecular motion. Silver is the best conductor of heat. If you stir a cup of hot coffee or tea with a pure silver spoon, the handle gets hot very fast. Styrofoam is one of the worst conductors, therefore it is used as a heat insulator.
Ceiling fans fight convection by blowing the hot air back down to the living space below.
Most of the heat we get comes from the sun by radiation. Sunlight amounts to about one kilowatt of heat per square meter of the earth's surface. A Calorie is 1000 calories, and should always be called a kilocalorie, but it is common practice in food labeling and nutritional references to simply call it a Calorie. The food Calorie is the kilocalorie. A calorie is the quantity of heat required to raise the temperature of one gram of water, one Celsius degree.