In plain English
What Market order means
A market order says, in effect, “execute now.” For a forex buy order, the relevant available price is normally the ask; for a sell order, it is normally the bid. In a fast-moving or thin market, available liquidity may change before the order is filled. A larger order can also be filled in pieces at different prices.
Why it matters
Market orders are useful when entering or exiting promptly matters more than controlling the exact price. They expose the trader to slippage, especially around economic releases, market opens, or periods of limited liquidity. “Best available” does not mean the last chart price, and it does not guarantee a particular fill price.
Example
EUR/USD is quoted at 1.0840/1.0842. A trader submits a market order to buy 100,000 euros. If the 1.0842 ask is no longer available when the order arrives, the order might fill at 1.0844 instead. The simplified example shows 2 pips of adverse slippage; the actual result depends on available liquidity.
Quick answers
Common questions
Does a market order guarantee execution?+
It generally seeks immediate execution while there are available counterparties, but it does not guarantee a particular price. In unusually disrupted conditions, a broker or venue may apply product-specific limits, reject the order, or execute only part of it.
Is a market order the same as buying at the chart price?+
No. A chart may show a last, mid, bid, or other reference price. A market buy normally executes against available asks, while a market sell normally executes against available bids.
Sources