The VIX - a measure of implied volatility of S&P 500 options commonly known as the "fear gauge" - shot up 30% today, marking the biggest daily gain since April as the stock market completed its biggest two-day slide since June.
Business Insider/Matthew Boesler (data from Bloomberg)
The VIX typically goes up when the stock market goes down. Today's action may suggest a near-term bottom in the stock market.