A market order instructs the broker to buy or sell immediately at the best currently available price, prioritizing speed of execution over price certainty. It's the fastest way to enter or exit a position, but in fast-moving or thin markets it can suffer slippage since the fill price may differ slightly from the price shown when the order was sent.
Market orders are the default order type most traders use to act on an immediate signal, as opposed to pending orders that wait for the price to reach a specific level.
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How Execution Models Work: ECN, STP and Market Maker
Market maker, STP and ECN describe where the other side of a trade comes from — and what each model changes about spreads, requotes and order handling.