VIX, the CBOE Volatility Index®, is a key measure of market expectations of near-term volatility conveyed by S&P 500 stock index option prices. Since its introduction in 1993, the VIX Index has been considered by many to be the world's premier barometer of investor sentiment and market volatility. Several investors expressed interest in trading instruments related to the market's expectation of future volatility, and so VX futures were introduced in 2004, and VIX options were introduced in 2006.
Options and futures on volatility indexes are available for investors who wish to explore the use of instruments that might have the potential to diversify portfolios in times of market stress.
Data definition and further information are available here (VIX)