Market order:
A market order is an order to buy or sell a security at current market prices. Once the order is placed, it executed immediately. The important feature of a market order is that it guarantees the execution of the order. However, the price at which the order is to be executed cannot be guaranteed.

This is because the market is volatile; prices fluctuate ever second. And the last-traded price in the market may have already changed by the time you bid your order. However, you would receive a price that is closer to your bid price, provided the stock you’re buying is a well traded or “liquid” stock.

Limit order:

A Limit order allows you to place an order in a security at the price you want. So, a buy limit order means you are ready to buy the security at a specific price or lower. And a sell limit order means you wish to sell the security at the limit price or higher. There is however no guarantee that this order will get executed, unlike Market Orders.