Temperature scales are used, obviously, to measure degrees of temperature, which is a measure of how much energy is being transferred from one molecule of substance to another. The Fahrenheit scale is from the English system of measurement, and is the one we use as a general rule in the United States. We continue to use it because we are comfortable with it, we grew up with it, and it is what we are used to. If I say my den is a comfortable 72 degrees Fahrenheit, most people know what temperature reading that represents. Celsius, on the other hand, is easier to work with, representing a scale of tens, where water freezes at 0 degrees and boils at 100 degrees. It is a product of the metric system, the system in use by the rest of the world, and is used as a whole by the scientific community. Kelvin is the temperature used to measure molecules as they cease to vibrate at all, what is called "absolute zero". This reading is much lower than Celsius or Fahrenheit. 0 degrees Kelvin is equivalent to -273.15 degrees Celsius, which is equivalent to -459.68 degrees Fahrenheit.