VIX is the trademarked ticker symbol for the CBOE Volatility Index, a popular measure of the implied market volatility of S&P 500 index options. The VIX index has been calculated by the Chicago Board Options Exchange (CBOE) since 1993.
It is often referred to as the fear index or the fear gauge. The VIX projects a range of the expected stock market volatility over the next 30-day period. It is used by traders, institutional investors, and hedge fund managers to diversify portfolios and correlate returns.