If you price an out-of-the-money put and an out-of-the-money call equally far from the current price, the put is usually more expensive - it carries higher implied volatility. That asymmetry is volatility skew. Left uncorrected, it would look like a pricing error. It is not; it is the market pricing fear.

Why downside costs more

Markets fall faster than they rise. Crashes are violent and correlated; rallies grind. Because the tail risk to the downside is larger, demand for downside puts - as protection - is structurally higher, and that demand bids up their implied volatility. The skew is the market's memory of every gap-down it has ever seen.

Reading the shape

A steep skew - downside puts priced far above upside calls - signals elevated fear and hedging demand. A flatter skew signals complacency. When skew steepens sharply, someone is paying up for protection; when it flattens into a rally, the crowd has stopped worrying. The shape shifts with regime, and the shift itself is information.

Skew is the price tag on fear - and it is almost never symmetric.

Why it matters to you

Skew affects what you pay. Buying downside protection is expensive precisely when you want it most. It also feeds into dealer positioning and how the tape behaves near key levels. You do not need to trade skew directly to benefit from understanding it - just from knowing that "cheap" and "expensive" options are rarely priced the way distance-from-strike alone suggests.