Volatility is the key to understanding market behavior.
Volatility is the change in price and thus, by definition, is directly related to price. This is expressed in the same units as the underlying contract or issue we are trading. Specifically, the true closing range tells us the maximum theoretical amount of money we could have made or lost between the close of one bar to the next. Thus, it is easier for a stock or commodity trader to relate to than a percentage measurement. As traders, our primary interest is volatility itself.