VIX Monthly Options
These options are based off the corresponding VIX futures. They are European-style exercise, and expire (cash settle) on Wednesdays. Since VIX futures often trade at discounts to “cash” VIX, a VIX option can trade at what looks like less than parity to the actual VIX.
If you want to trade VIX options, get comfortable with all that, and the fact that you need to price the volatility of a volatility index.