Volatility is just a statistical term to measure the tendency of the market to fluctuate. Big fluctuations suggest fear, because they mean that investors are frantically changing their minds about what stocks are worth, in the face of great uncertainty. Smaller fluctuations suggest that investors are confident and they know what the stocks are worth.

The standard deviation of percentage changes in price is used to calculate observed volatility. Volatility can be observed by looking at past changes in stock price. For example: A stock whose price went up 10% yesterday and went down 25% today is more volatile than a stock which increased 2% in both days. A higher volatility means that a security's value can potentially be spread out over a larger range of values. This means that the price of the security can change dramatically over a short time period in either direction. A lower volatility means that a security's value does not fluctuate dramatically, but changes in value at a steady pace over a period of time.

Volatility Index (VIX) is a measure of market's expectation of volatility over the near term. In simple words, Volatility Index (calculated as annualized volatility, denoted in percentage e.g. 20%) is a measure of the amount by which an underlying Index is expected to fluctuate based on the order book of the underlying index options. VIX is the ticker symbol for the Chicago Board Options Exchange Volatility Index, a popular measure of the implied volatility of S&P 500 index options. It is commonly called the VIX, and is often referred to as the "fear index." India VIX is a volatility index based on the Nifty 50 Index Option prices. From the best bid-ask prices of Nifty 50 Options contracts, a volatility figure (%) is calculated which indicates the expected market volatility over the next 30 calendar days. i.e. higher the India VIX values, higher is the expected volatility and vice-versa.

Volatility is different from implied volatility, in the sense that volatility is observed by looking at past data, whereas implied volatility represents expectations about future fluctuations. Volatility expectations, or implied volatility, are deduced from option prices (both call and put) on the underlying security -- since these expectations are reflected in market prices of the option. Higher fluctuation expectations mean that the option has a greater probability of ending in the money (ITM) and thus the option commands a higher price and vice versa. By inputting the option price, along with other variables such as maturity, interest rate, strike price and underlying security price, in a pricing model (e.g. Black-Scholes) it is possible to derive an estimate of the investor's expectation of future volatility. Generally, implied volatility increases when the market is bearish & decreases when the market is bullish

The VIX will measure the market's expectation of Nifty/Sensex volatility over the coming month (30-day period). The first VIX, introduced by the CBOE in 1993, was a weighted measure of the implied volatility of eight S&P 100 at-the-money put and call options. Ten years later, it expanded to use options based on a broader index, the S&P 500, which allows for a more accurate view of investors' expectations on future market volatility.

India VIX is a volatility index based on the Nifty 50 Index Option prices. From the best bid ask prices of near term Nifty 50 Options contracts (which are traded on the F&O segment of NSE), a volatility figure (%) is calculated which indicates the expected market volatility over the next 30 calendar days. Calculation: Higher the implied volatility higher the India VIX value and vice versa. There are some differences between a price index, such as the Nifty 50 and India VIX. Nifty 50 is calculated based on the price movement of the underlying 50 stocks which comprises the index. India VIX is calculated based on the bid-offer prices of the near and mid month Nifty 50 Index Options. Nifty 50 Index is an absolute number, e.g. 4500, 5000 etc., whereas India VIX is a percentage value (e.g. 20%, 30% etc.).

Whereas Nifty 50 signifies how the markets have moved directionally, India VIX indicates the expected near term volatility and how the volatility is changing from time to time. India VIX is a premier barometer of investor consensus of market volatility expressed through option pricing. VIX is a trademark of CBOE Incorporated and Standard and Poor’s has given license to NSE, with permission from CBOE, to use this trademark in the name of India VIX and for purposes relating to India VIX.

The VIX is often referred to as the "Fear Index". The exact number given by VIX is what a statistician would call the "forecasted annualized standard deviation of returns."

A VIX reading of 50 means that options prices are suggesting that, over the next year, stock prices are expected to fluctuate within a range of plus or minus 50%. A VIX reading of 20 would mean expectations that the market will fluctuate less, staying within a range of plus or minus 20%. In most cases, a high VIX reflects increased investor fear or uncertainty and a low VIX suggests complacency or less stressful times. Historically, this pattern in the relationship between the VIX and the behavior of the stock market has repeated itself in bull and bear cycles. During periods of market turmoil, the VIX spikes higher, largely reflecting the panic demand for puts as the hedge against further decline in stock portfolios. During bullish periods there is less fear and therefore less need for portfolio managers to purchase puts. By measuring investor fear levels tick by tick and day by day, the VIX, like many emotional gauges (e.g. put/call ratio (PC Ratio), means a ratio of the trading volume or open interest of put options to call options) can be used as a contrary opinion tool in attempting to pinpoint market tops and bottoms on a medium-term basis. There are two ways to use the VIX in this manner. The first is to look at the actual level of the VIX to determine its stock-market implications. Another approach involves looking at ratio comparing the current level to the long-term moving average of the VIX.