Module 3 — Placing an Order | How Markets & Businesses Work

Module 2 showed the machine: bids, asks, a gap between them. An order is your instruction for how to engage that machine, and the three basic types — market, limit, stop — differ in one dimension only: certainty of execution versus certainty of price. The definitions below track the SEC's own investor education (linked throughout); the commentary on when each bites is the trading craft.

The three instructions

Market order — "fill me now." Executes immediately at the best available price. Per the SEC's framing: execution is guaranteed, price is not. In a liquid stock on a calm day, you'll pay about the ask and it's fine. In a thin stock, at the open, or in fast conditions, "best available" can be far from the last print you saw — the order walks down the book until it's filled. Market orders are how beginners discover slippage.

Limit order — "fill me at my price or better." A buy limit executes only at your limit price or lower; a sell limit at your price or higher. Price is guaranteed; execution is not — if the market never comes to you, you simply don't trade. That "miss" is the fee for price certainty, and professionals overwhelmingly pay it: a limit order can't be surprised.

Stop order — "if it gets there, get me out (or in)." Dormant until price touches your stop level, then it becomes a market order. A sell stop below the market is the classic protective stop-loss; a buy stop above the market is how breakout traders automate entries (T4 territory). The fine print, straight from the SEC's stop-order bulletin: once triggered, it's a market order — in a gap or a fast market it can fill well beyond your stop price. A stop-limit variant caps that by becoming a limit order instead, at the cost of possibly not filling at all while price runs away — the one scenario a protective stop existed to prevent.

Choosing: what are you actually afraid of?

The selection logic compresses to one question. Afraid of missing the trade? Market order (and accept slippage as the fee). Afraid of overpaying? Limit order (and accept missing as the fee). Afraid of catastrophe while you're not watching? Resting stop order (and accept that gaps can jump it). Every "advanced" order type on a broker's menu — trailing stops, brackets, one-cancels-other — is a combination of these three fears automated.

Note what this module quietly is: your first risk-management lesson. The Turtles' "non-negotiable" exits, Darvas's trailing box stop, O'Neil's fixed-percentage cut — all of them, mechanically, are stop orders or the discipline of simulating one. The psychology of actually honoring them is the next course's business; the plumbing is now yours.

Reference page: Order types. Official sources: Investor.gov's Types of Orders, the Understanding Order Types and Stop Orders bulletins, and FINRA's order-type guide.

Assignment

In a paper-trading account (every major broker offers one free), place all three order types on the same liquid stock: a market order, a buy limit 1% below the current price, and — once filled — a sell stop 2% below your entry. Watch what each does for a day. Then write the three-fears sentence for your own temperament: which miss would genuinely bother you most? Your honest answer predicts most of your future order tickets.

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