Two very different numbers share the name volatility. Realized volatility is a fact — the annualized wiggle of returns that already happened. Implied volatility is a price: the vol number that makes Black–Scholes match what option buyers actually paid. IV is the market's forecast of movement, plus a markup set by sellers who must pay out if they're wrong.
That markup is the variance risk premium: across most equity indices, most of the time, implied volatility has historically run a few points above the realized volatility that follows. It exists for the same reason hurricane insurance costs more than its actuarial fair value — buyers pay up for certainty, sellers demand rent for carrying open-ended risk. Collecting that gap is the premium seller's structural edge.
The edge inverts in two mirror-image scenarios: storms nobody priced (a long calm compresses IV, then volatility erupts — February 2018, February 2020) and priced storms that fizzle (post-panic IV at 45% while the market cools to 26% — historically the fattest gap sellers ever collect). Both can show the same IV number on your screen, which is why the raw level tells you almost nothing.
In practice, compare IV to itself with IV rank (where today's IV sits in its own 52-week range) and IV percentile (the share of days that closed with lower IV), then sanity-check against the realized trend. The lesson's interactive explorer draws the IV cone against a simulated realized path so you can watch the seller's edge — and the seller's bad month — form in real time.
Educational, not investment advice.