The CBOE Volatility Index or VIX is often also called the 'fear' index.
The Chicago Board Options Exchange (CBOE) developed the index which measures the near term (next 30 days) expected volatility of S&P 500 Index options trading.
The CBOE Volatility Index or VIX as it is commonly referred to, is often seen as the best gauge of 'fear' and uncertainty in the market.
During periods of financial stress, which are often accompanied by steep market declines, option prices and the VIX tend to rise. The greater the fear, the higher the VIX level.
As investor fear subsides, option prices tend to decline, which in turn causes VIX to decline.
We update this chart daily after the close of US markets. The dates in this chart are US trading dates.