In trading, a market order is an order placed by an investor to a broker ordering a purchase at the going market price. Market orders are executed immediately as long as there is a willing seller or buyer. They are the least complex of all order types.
Highly liquid securities and securities in which clearing houses, exchanges or brokers act as central counterparties to trades can typically be bought or sold immediately at the going rate using market orders. Less liquid assets may require time to buy or sell, and may be bought from different sellers at different prices, or be sold to different buyers at different prices. This makes market orders particularly disadvantageous for investors looking to profit from small fluctuations in market rates. But market orders carry a certain amount of risk for all investors because it is possible that prices will climb rapidly before a market order is fulfilled, making the purchase more expensive and reducing the chance of capital gains.
Example: An investor wants to buy shares in a specific company. Because they expect to invest in the company long term (as opposed to short term investment or day trading), they are not concerned about the exact price which they will pay for the shares. They simply want to buy the shares as soon as possible at the best available offer. The investor places a market order with their broker, which buys the shares at the best offers available until they have bought the full number of shares requested and the order is fulfilled.
Limit orders provide a more secure alternative to market orders because they allow investors to specific the exact amount which they are willing to pay for a security or which they are willing to sell a security for.