Order types and how they behave in a live market

Every order you send resolves a single tension: do you want certainty about the price, or certainty that the trade happens at all? You cannot have both. A market order guarantees execution and accepts whatever price the book offers. A limit order guarantees the price and accepts that it may never fill.

Once you frame order types this way, the choice stops being a menu item and becomes a decision about what matters more in the moment you are trading.

A market order crosses the spread immediately and takes liquidity from the opposite side of the book. In a deep market with tight spreads, the difference between the price you saw and the price you got is negligible. In a thin market, or during a news release, that difference — slippage — can be material.

A limit order rests in the book at your chosen price and only fills if the market comes to you. It adds liquidity rather than taking it, and it never pays more than the level you set. The cost is uncertainty: the market can trade through your level in a fast move and leave you unfilled.

A stop order sits dormant until the market reaches a trigger price, at which point it becomes a market order. It is the standard tool for exiting a position that has moved against you. Because it converts to a market order on trigger, a stop can fill worse than its trigger level in a gap.

A stop-limit variant converts to a limit order instead, which protects the fill price but risks no fill at all in exactly the conditions where you most want out.