This article was originally published in The Option Strategist Newsletter Volume 3, No. 21 on November 17, 1994.
Volatility is merely the term that we use to describe how fast a stock, future, or index changes in price. When we speak of volatility in connection with options, there are two types of volatility that are important: historical volatility, which is a number that can be calculated mathematically by seeing how fast the stock has been changing in price over the past 10 days, 20 days, or any other time period that we want to examine. The other type of volatility that is important for option traders is implied volatility. Implied volatility is what the options are "saying" about future volatility: if it is high, then the options are predicting that the underlying instrument is going to become more volatile in the (near) future; if it is low, then the options are predicting that the volatility of the underlying will decrease. Thus there may be a difference between the historical and implied volatility. If the difference is large enough, then one can use options strategies to create a position with an "edge" — the "edge" being the differential between these two types of volatility.
