Investing foundations
A market order asks to buy or sell at the best available prices. It usually favors getting the trade completed quickly, while the final price remains uncertain. A limit order sets a price boundary: the highest price you will pay to buy, or the lowest you will accept to sell. It may remain partly or entirely unfilled.
This lesson explains that trade-off with fictional numbers. You can practice on paper without buying an investment, opening an account, or using a paid tool. The examples describe ordinary U.S. stock orders; local rules and broker services can differ.
A market order accepts the available prices
An order is an instruction to buy or sell. Execution, also called a fill, means a trade actually takes place. A broker is a firm that handles your instruction and arranges its execution.
During normal market conditions, a market order generally executes quickly when buyers and sellers are available. It does not fix the price. Investor.gov explains this execution-versus-price trade-off.
A market order also does not promise an instant or complete trade in every situation. Prices and available quantities can change while the order is being handled. A trading halt, meaning a temporary pause in trading, or a shortage of willing buyers or sellers can prevent immediate execution. FINRA explains trading interruptions.
A limit order sets a boundary for each share
A buy limit of $20.10 permits execution at $20.10 or less per share. A sell limit of $19.90 permits execution at $19.90 or more. These are boundaries, so a fill can occur at a better price. Investor.gov defines buy and sell limits.
The limit applies to the share price, before separate fees or taxes. It does not guarantee that a trade happens or that every requested share trades. A buy limit also does not protect the investment from falling after purchase.
Read the bid and ask alongside the last price
The bid is the highest quoted buying price; the ask, or offer, is the lowest quoted selling price. The bid-ask spread is the gap between them. Quotes apply to particular share quantities. Investor.gov explains the bid, ask, and spread.
A last-traded price reports an earlier transaction. A chart’s closing price shows the final price recorded for a completed period. Neither promises the price available for a new order. For that chart distinction, revisit how to read a stock chart.
Slippage describes the difference between an expected reference price and the actual execution price. Execution can be worse or better than that reference. The spread compares buying and selling quotes at one moment; slippage compares a reference with a later fill. The SEC explains why execution prices can differ from displayed quotes.
Compare three fictional instructions
Imagine River Street Bakery stock last traded at $20.00. Its current best bid is $19.90 and best ask is $20.10. The spread is $0.20 per share.
For this simplified teaching example, suppose four shares are available to buy at $20.10 and another six at $20.30. Those are the only available offers, they stay unchanged, and no competing orders arrive. Ignore fees and taxes. Compare these separate instructions to buy ten shares:
| Instruction | Illustrated result |
|---|---|
| Market order | Four shares at $20.10 plus six at $20.30. All ten trade. |
| Limit order at $20.10 | Four shares at $20.10. Six remain unfilled. |
| Limit order at $20.00 | No shares trade because no seller offers that price or less. |
The market order costs (4 × $20.10) + (6 × $20.30) = $202.20, averaging $20.22 per share. Using the displayed $20.10 ask as the reference, ten shares would have cost $201.00. The illustrated slippage is $1.20 in total, or $0.12 per share on average.
The $20.10 limit order spends $80.40 for four shares. It cannot buy the other six at $20.30. If suitable offers appear while it remains active, more shares might fill; otherwise, they remain unfilled. The $20.00 last trade does not supply an available seller at that price.
Real orders can have different results. The SEC’s order-types bulletin explains that parts of a market order can execute at different prices and that limit orders do not guarantee execution.
Fictional offers: 4 shares at $20.10 + 6 shares at $20.30
●●●● ●●●●●●
10 shares filled
$202.20 total
$20.22 average per share
●●●● ○○○○○○
4 filled; 6 unfilled
$80.40 spent
No buying above $20.10
○○○○ ○○○○○○
0 filled; 10 unfilled
$0 spent
No offer at $20.00 or less
● Filled share · ○ Unfilled share. Each instruction is a separate example. Offers stay unchanged; no competing orders, fees, or taxes.
Check how much filled and when the order expires
A partial fill means only some requested shares traded. A price touching your limit on a chart does not prove that your whole order filled. The completed quantity and remaining quantity answer that question.
Time in force means how long the instruction remains active:
- Day: an unfilled order generally expires at the end of that trading day. Regular and extended-session handling depends on the broker’s terms.
- Good ’til canceled (GTC): the order can stay active beyond one day, until filled, canceled, or the broker’s expiration deadline. It does not stay open forever.
FINRA explains partial fills and time-in-force options. Different instructions can change what happens to an unfilled balance. Check actual terms rather than assuming a default.
A stop price is a trigger
A stop order becomes a market order when its stop-price condition is met. The stop price is the activation point, not a guaranteed selling or buying price. A stop-limit order activates a limit order instead, so it can remain unfilled if available prices move beyond the limit.
For a fictional sell stop at $18, a sudden price drop could lead to execution below $18. Adding a limit would set a selling-price boundary but might prevent a sale. Brokers’ trigger standards and available order types differ. The SEC’s stop-order bulletin explains these risks.
Practice one question on paper
Using the bakery example, explain what happens to a ten-share buy limit at $20.10. For this exercise, make it a Day order with no extended-session instruction. Your answer should identify the $80.40 completed purchase, the six remaining shares, and the unfilled balance generally expiring at the end of the regular trading day. Then explain why a $20.00 chart price alone cannot answer whether that order filled.
The goal is to recognize the uncertainty each instruction accepts. Choosing an order type cannot establish whether an investment suits someone’s goals or is reasonably valued.
For the wider money question, return to a simple money plan before investing. To compare exchange trading with mutual-fund pricing, read stocks, mutual funds, and ETFs.
Educational content only, not a recommendation to buy, sell, or hold an investment. Investing involves risk, including possible loss of principal. All worked examples are fictional and exclude fees and taxes. Order availability and handling vary by broker and market. Sources checked October 13, 2026.