How currency trading is done traditionally

Currency trading is always done with currency pairs, such as EUR/USD, and so it is useful to consider the currency pair as an instrument, which can be bought or sold.

• Buying the currency pair implies buying the first, base currency and selling (short) an equivalent amount of the second, quote currency (to pay for the base currency). (It is not necessary for the trader to own the quote currency prior to selling, as it is sold short.) A speculator buys a currency pair, if she believes the base currency will go up relative to the quote currency, or equivalently that the corresponding exchange rate will go up.
• Selling the currency pair implies selling the first, base currency (short), and buying the second, quote currency. A speculator sells a currency pair, if she believes the base currency will go down relative to the quote currency, or equivalently, that the quote currency will go up relative to the base currency.

After buying a currency pair, the trader will have an open position in the currency pair. Right after such a transaction, the value of the position will be close to zero, because the value of the base currency is more or less equal to the value of the equivalent amount of the quote currency. In fact, the value will be slightly negative, because of the spread involved.

In todays currency market, a trade goes through a three-step process:

1. the trader communicates the currency pair and the amount he/she would like to trade with another dealer.
2. the dealer responds with a bid and an ask price
3. the trader responds to the bid and ask price with one of:
   1. buy (by saying "Mine" or "I buy" or "I take")
   2. sell (by saying "yours" or "I give you" or "I sell")
   3. refuse.

The transaction occurs if the final response is either a buy or a sell. The dealer is required to quote a "good" market price, since he does not know whether the trader will buy or sell.

The currency exchange market described above is referred to as the spot market and the transaction described is referred to as a spot deal. A spot deal consists of a bilateral contract between a party delivering a specified amount of a given currency against receiving a specified amount of another currency from a second counter party, based on an agreed exchange rate, within two business days of the deal date, which is referred to as the settlement date. (The settlement date for USD/CAD is one business day after the deal date.) Speculators rarely deliver, however. Instead, they use what is referred to as a rollover swap. The rollover swap is designed to allow the changing of an old deal date to the current date by simultaneously closing an open position for todays date and opening the same position for the next day at a price reflecting the interest rate differential between the two currencies.

When a trader buys or sells a currency pair, the value of the currency pair, as an instrument, initially is close to zero. This is because (in the case of a buy) the quote currency is sold to buy an equivalent amount of the base currency. As the market rates fluctuate, however, the value of the currency pair position held will also fluctuate. Thus, if the rate for the currency pair goes down, the speculators long position will lose in value and become negative. To ensure that the speculator can carry the risk for the case where the position results in a loss, banks or dealers typically require sufficient collateral to cover those losses. This collateral is typically referred to as margin.

To limit down-side risk, traders often specify a Stop-Loss rate for each open trade. The Stop-Loss specifies that the trade should be closed automatically when the currency exchange rate for the currency pair in question reaches a certain threshold. For long positions, the Stop-Loss rate is always lower than the current exchange rate; for short positions, it is always higher. Traders, at times, also specify a Take-Profit rate for their trades in order to lock in a profit when the exchange rate reaches a certain threshold. For long positions, the Take-Profit rate must be above the current rate, while for short positions, it must be below the current rate.

A trader may also leave an order with a bank, broker or dealer. These so called leave orders are orders that a trade should be executed (in the future) when certain market conditions occur. There are three types of leave orders:

1. entry orders: specifies that a currency pair should be traded when it reaches a certain exchange rate. Entry orders are used when the trade would not offset a current position.
2. take-profit orders: are used to clear a position by buying (or selling) the currency pair of the position when the exchange rate reaches a specified level.
3. stop-loss orders: are used to clear a position by buying (or selling) the currency pair of the position when the exchange rate reaches a specified level.

http://fxtrade.oanda.com/currency_trading/intro_currency_exchange.shtml