It does not guarantee that your order will be executed even if your price has been reached. Orders are queued while being bought or sold. For Example. Assume you placed a Buy limit order of 100 Rs for the ABC script. Let’s say there are 100 buyers and 50 sellers waiting to trade in ABC at 100. ABC is currently trading at 105 Rs and after a few minutes, it reaches 100 Rs. Since there are only 50 sellers for 100 Rs, only 50 buyers will be able to buy the script once this price is reached. As for the other 50 buyers, they’ll have to wait until more sellers become available.