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https://corporatefinanceinstitute.com/resources/knowledge/trading-investing/vix-volatility-index/

A snippet

A high VIX indicates high expected volatility and a low VIX number indicates low expected volatility.

History of the VIX

The long-term average for the VIX volatility index is 18.47% (as of 2018).

Historically speaking, a VIX below 20% reflects a healthy and relatively moderate-risk market. However, if the volatility index is extremely low, it may imply a bearish view of the market.

A VIX of greater than 20% signifies increasing uncertainty and fear in the market and implies a higher-risk environment. During the 2008 Financial Crisis, the volatility index skyrocketed to extreme levels of above 50%. That meant that option traders expected stock prices to fluctuate widely, between a 50% upswing or downswing within the next year, 68% of the time. At one point during the crisis, the index reached as high as 85%.

Although VIX levels can be very high during times of crisis, extreme levels are rarely sustained for extended periods of time. This is because the market conditions lead traders to take actions to reduce their risk exposure (such as purchasing or selling options). That, in turn, reduces the levels of fear and uncertainty in the market.