Implied volatility (IV) is the market's forward-looking estimate of future movement; historical volatility (HV) is what actually happened in the past. For a day trader, IV usually matters more — because it prices your options right now (see realized vs. implied volatility).
The difference
HV (a.k.a. realized volatility) is backward-looking — it measures how much price has moved over some past window. IV is forward-looking — it's derived from current option prices and reflects how much the market expects price to move going forward. IV is what's embedded in the premium you pay today; HV is a historical fact. One is the price of the future; the other is a record of the past.
Why IV matters more for a day trader
When you buy an option, you're paying for implied volatility — high IV means expensive options, low IV means cheap ones. So IV directly affects your cost and your exposure to IV crush (if IV drops after you buy, your option loses value even if you're right on direction — the classic “right but lost” trap). HV is useful context (comparing IV to HV tells you if options are “expensive” or “cheap” relative to actual movement), but IV is the number that hits your P&L today.
You pay for implied volatility, not historical. HV is the rear-view mirror; IV is the price tag on the windshield — and it's the one your wallet feels.
The quick takeaway
IV (forward-looking, prices your options now) usually matters more to a day trader than HV (backward-looking). Watch IV for cost and crush risk; use HV as context for whether IV is rich or cheap. NoVo factors the volatility environment into its read and execution — because what you pay in IV, and the crush that can follow, are real parts of every options trade.