When a trader takes a ‘long’ position, the trader is placing a ‘Buy’ order, likewise, when a trader takes a ‘short’ position, the trader is placing a ‘Sell’ order. For example, if you go ‘long’ on an AUD/USD you are buying AUD in anticipation that it will rise against the USD, conversely, if you go ‘short’ on AUD/USD you are selling AUD in anticipation that it will lower against the USD.