When one goes short, it means that you are just placing a selling order on the pair of currency. In trading all the pairs of currency have quote currency and base currency.The quote generally looks like JPY/USD= 100.00. USD is regarded as a base currency whereas JPY is known as quote currency. This particular quote depicts the rate of nearly one US dollar which is equal to hundred Japanese Yen. When one places short trade on the pair of currency they will move short on USD dollar and move a long way on Yen.
It seems to be complicated, but one will make this particular deal of that the value of one dollar.
Go short = sell
Go long = buy