The order screen lists several unfamiliar names. Here is what each order type guarantees and what it gives up.
Every order type balances two things: getting the price you want and getting filled when you want. No order guarantees both perfectly. Insist on price and you may not get filled; insist on a fill and the price may slip. The many names on an order screen are simply different points along that trade-off. Which one to pick depends on whether price or execution matters more to you right now.
The most basic order, where you set the price yourself. A buy fills only at that price or lower, a sell only at that price or higher. The price is protected, but if the market never reaches it the order sits unfilled. Partial fills, with the rest left waiting, are common. Unfilled orders expire at the end of their validity period, or, if you set a long one, stay live and may fill while you have forgotten about them.
An order with no price, filled immediately against whatever the other side is offering. It is used when speed matters, but the price is not guaranteed. If your size exceeds what sits at the best price, the order works through the next levels and your average price worsens. In thinly traded stocks, or at thin moments such as right after the open, it can slip much further than expected.
Many markets collect orders before the open and just before the close and match them at a single price in an auction. In Korea, a conditional limit order works as a limit order during the session and, if still unfilled at the end, converts to a market order in the closing auction. It suits someone who wants to aim for a price during the day but must finish the trade that day. The catch is that the final fill has no price limit, so an unfavourable closing price has to be accepted. Check the exchange's and broker's official guidance for auction times and detailed rules.
Some markets, including Korea, offer limit orders whose price is set automatically from the order book at the moment you submit, rather than typed in. Their names sound alike and are often confused, but they reference different sides of the book.
Sometimes you can attach an immediate-execution condition. Immediate-or-cancel (IOC) fills whatever quantity is available right away and cancels the rest. Fill-or-kill (FOK) fills only if the entire quantity can be filled at once and otherwise cancels the whole order. Both stop a resting order from filling at a moment you no longer want. Stop orders, which are sent when price touches a set level, are common in overseas markets too, but they do not guarantee the fill price at that moment either.
Order mistakes usually happen when you rush or are unfamiliar with the screen. They become more frequent when every market's layout is different, as in many apps for overseas stocks.
Deciding first what matters most makes the choice simple. If price matters, consider limit-type orders; if you must finish that day, conditional ones; if immediacy matters most, market-type ones. Brokers differ in the order types and names they offer and in trading-hour rules for overseas markets, so test an unfamiliar order with a small quantity first. This article explains how orders work, does not recommend any trade and is not investment advice.
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