In short VIX measures velocity of changing prices in near-dated options, so it's often referred to as the "fear gauge". Low VIX means stable market, high VIX means capital is shifting about. In equities/bond markets, low VIX has been the goal/result of central banks QE policies propping up markets. Yesterday possibly signals the long awaited shift in this decade long trend.

Please read this article I've written on volatility for more info.

https://steemit.com/cryptocurrency/@maven360/volatility-you-vixen-why-vol-is-crypto-s-best-friend