If temperature is the kinetic energy per molecule, then heat can be thought of as the sum of the kinetic energy of the molecules. This can also be thought of as the thermal energy of the substance. Boiling water is 100 ° C. I would rather spill one drop of water on my skin then 1 gallon. Why? The gallon of water has more molecules of water and therefore more thermal energy.
Heat is more often associated with thermal energy transfer. Since heat is a form of energy, the correct SI unit is the Joule. A calorie is a more common unit. A calorie is defined as the energy required to raise 1 gram of water 1 ° C. One calorie is the equivalent of 4.184 Joules (1 cal = 4.184 J). The calories you see on your cereal packages are the equivalent of kilocalories and are sometimes given the unit Cal. It seems a little silly but you can’t expect Cheerios to give a lesson on units. (1 kilocalorie = 1000 calories = 1 Cal)