The quote everything starts from
Lesson 2’s worked quote — bid $49.95 for 200 shares, ask $50.05 for 300 — and the four things an order can do against it. A limit order does not always wait, and not every trade crosses the spread the same way: it depends on whether the order is marketable.
| Order placed | What happens |
|---|---|
| Marketable limit — buy 100 at $50.05 | Fills at once at the ask: 100 × $50.05 = $5,005. Sellers are already posted at or below the limit, so the order executes immediately — and pays the crossing toll (the spread). |
| Nonmarketable (resting) limit — buy at $50.00 | Rests in the book. It fills only if a seller comes down to $50.00 — and it may never fill. |
| Limit — buy 400 at $50.05 | Partial fill: the 300 shares offered at $50.05 fill; the remaining 100 rest. Fills can arrive in pieces, and the rest may never come. |
| Limit — buy at $49.90 | No fill that day if no seller meets it. A limit caps the price you will accept; it never promises a trade. |
The order types, by what they promise
| Order | It promises | It does not promise |
|---|---|---|
| Market order | Execution, at the market’s next available prices | The price |
| Marketable limit | Executes at once against what is posted at or inside the limit, never worse than the limit | The best price — it crosses the spread |
| Nonmarketable limit | Never worse than the limit | A fill at all |
| Stop-market | Once triggered, it becomes a market order and executes | The stop price — a gap can fill far through it |
| Stop-limit | Never executes worse than its floor price | Execution — on a gap-through it may never fill; nonexecution is the design, and the position and loss stay open |
| Close-based exit (the course’s rule) | A trigger you can check after the bell: the daily close | The closing price itself — the exit happens at the next session’s available price, so overnight gap risk is the cost |
A stop is an exit instruction, not a floor under your loss: every mechanic above can deliver less than the tidy number in the plan when the market gaps.
Costs are not taxes, and sessions change the fill
Transaction costs are paid on the trade itself: the spread (what a marketable order pays to cross, what a resting order can earn) and any commission. Taxes are a separate, later obligation on profits — not a cost of the transaction. In extended hours the same order types meet thinner books and wider spreads, partial fills get likelier, and the regular session’s patterns are tendencies, not laws.
Keep the set
The other reference sheets: Instrument comparison · Risk arithmetic · Financial statements · Reading an edition. All five hang off the Education hub.
Summarizes Lesson 2, Lesson 20 and Trade-track Lesson T5, as reviewed October 24, 2026.