When the S&P 500 plunges, the VIX typically spikes as investors panic-buy insurance (options).

4 VIX Trading Strategies to Effectively Manage Market Volatility

What is the VIX Volatility Index and How Do You Trade it? - IG

However, you can trade the sentiment it represents. Here is the reality of "investing" in the market's fear. 1. You Aren't Buying a Stock, You’re Buying Expectations

What is the Volatility Index (VIX)? The VIX is a real-time volatility index, created by the Chicago Board Options Exchange (CBOE). www.ig.com