Limit order is a request by a trader to execute a transaction at a specified price or better. That means that Long Limit order will be executed at the limit price or lower. And Short Limit order will be executed at the limit price or higher.
It’s important to understand that many CFD platforms have a slight distinction in how Limit order is defined. They allow a trader to set a limit price and when the specified limit price is reached, a limit order becomes Market order. At that point, it is fulfilled at the current market price. Hence, even with a Limit order, a certain level of slippage (the difference between the expected price and the order execution price) is possible. The slippage is usually lower in the liquid and less volatile markets.
By nature, Limit order gives a trader more control over the price but does not guarantee the order execution. The limit price might not reach at all. In situations where the speed of execution is more important than the price of execution, Market order may be more suitable.