Limit orders are designed to give you more control over the buying and selling prices of your trades. Prior to placing a Limit buy order, a maximum acceptable purchase price amount must be selected, and minimum acceptable sales prices are indicated on Limit sell orders.
With a Limit order; you place an order on the order book at a Limit Price you define, in hopes that it’ll be filled by someone else’s order. When the market price reaches your limit price, it’ll buy or sell (AKA “fill the order") if there is a counterparty available that wants to sell or buy.
Limit orders are not subject to slippage as you will buy or sell at a predefined price. You can set a limit buy or limit sell order, and you will have to pay a transaction fee; the so-called 'Maker Fee', which is typicaly lower than the 'Taker fee' for Market orders.
Example: Suppose you hold a Bitcoin (BTC) balance at Bullex and you want to buy DASH. In order to do so you go to the trading page for the DASHBTC pair. Under the chart you click on the tab 'Limit order' and you fill in the amount of DASH you want to buy. Now you also have to define yourself for which price (the so-called Limit Price) you want to buy DASH. Please check your order carefully before clicking 'Buy'.
Please note that a Limit order may never execute. If at any time there are no counterparties willing to buy or sell for the Limit Price that you have set, the order will never result in a transaction.
As long as you order has not been -partially- fulfilled it is possible to cancel your order. To cancel an open order, please visit the trading page for that specific trading pair, and scroll down. There you will find a section called 'Open orders'. Select the order you want to cancel. To the right you will see an option to click 'Cancel'.