Plain-English definitions of options terms. Each one is short: what it means, one worked example with play money, and where it bites. When a term has a lesson, the page points you to the simulator so you can feel it, not just read it.
Concepts
The price of the option itself: what buyers pay, what sellers collect, and why the quote moves your breakeven. One worked example with play money.
The line your option is measured against: how strike choice sets both the price and the odds, with three calls on the same stock compared side by side.
In, out, or at the money: what the labels really tell you, why puts flip the map, and why finishing in the money can still lose money.
Buy or sell, call or put: four shapes cover every options trade. Drag the expiry price and watch which shapes cap your loss and which cap your gain.
Options melt as days pass even when the stock stands still. See the melt in numbers and why waiting is the quiet way buyers lose.
When the seller of an option is forced to fulfill the contract: buy or sell 100 shares at the strike. One worked example, and why it surprises beginners.
The market's estimate of how much the stock will move, backed out of the option price. Why pre-earnings options are secretly expensive, and what IV crush does to winners.
Delta, gamma, theta, vega: the four gauges on an option position and what each one is telling you. One worked example, and why income sellers should reread the gamma row.