A market order is an instruction by an investor to a broker to buy or sell stock shares, bonds, or other assets at the best available price in the current financial market.

It is the default choice for buying and selling for most investors most of the time. If the asset is a large-cap stock or a popular exchange-traded fund (ETF), there will be plenty of willing buyers and sellers out there. That means that a market order will be completed nearly instantaneously at a price very close to the latest posted price that the investor can see.