Trades based on Limit or Stop orders can be postponed. They are postponed because trades on such orders are performed only when the order conditions are met. This does not require any additional involvement from the trader. The trades will be performed automatically.
You can use the Order module or the Click-Trade module to create these two types of trades. In the case of the Order module, you can create both types of these orders manually. In the case of Click Trade, you can use the Join Bid, Sell Bid, Join Offer, Buy Offer buttons to create Limit orders. For more details on using the Click Trade module, see Trading in the Click-Trade Module.