Market Order
An order to buy or sell immediately at the best available price. Guarantees execution but not the fill price.
A market order instructs your broker to execute a trade right now at whatever the current best price is. It is the fastest, most certain way to enter or exit a position.
The tradeoff is price uncertainty. In a liquid market the fill will be very close to the last traded price; in a thin or fast-moving market you can be filled significantly away from what you saw on screen — this gap is slippage.
Use market orders when certainty of execution matters more than the exact price — for example, cutting a loss quickly or entering a position just before a hard catalyst.
On the desk
Stock XYZ last traded at $50.00. You send a market buy order for 100 shares. The ask is $50.02 and you fill there. Your effective entry is $50.02, not $50.00.