An order is generally explained as an instruction to buy or sell. Limit orders are instructions to buy or sell assets at a specific or better price. This is the preferred transaction order employed when the execution price is given more consideration than the execution of the order.
With limit orders, execution is not guaranteed but it ensures that a buyer does not pay more than a pre-determined price for an asset and a seller does not accept less than a pre-determined price for an asset.
When placing a limit order, you must specify the price you are willing to buy or sell at, and your order is not executed until your price is matched.
Limit orders are placed on Guava trade page. See here for more on that.