Direct answer
Forex currency trading works by speculating on (or hedging against) changes in the exchange rate between two currencies shown as a pair (for example, Currency A/Currency B). A trader chooses a position direction—buying or selling the pair—then closes the position when the pair’s rate moves. The trade’s value is ultimately expressed in the trader’s account base currency, even if the traded pair uses different currencies.
How the market is represented
Forex rates are quoted as a currency pair: the first currency is the base currency of the pair, and the second is the quote currency of the pair. When the pair price rises, it means one unit of the pair’s base currency buys more of the quote currency; when it falls, it buys less. A position is defined by the pair, the number of units represented by the trade size, the entry and exit prices, and the account settings such as account base currency.
Mechanics: from order to profit/loss
To open a position, you typically submit an order through your broker or trading platform with an order type (for example, market or limit), a pair, a trade size, and a direction (buy or sell). The platform fills the order using available bid/ask prices. The spread (the difference between bid and ask) and any commissions directly affect the initial cost.
Profit and loss depend on the price difference between entry and exit, scaled by the trade size. Because your account base currency may differ from the currencies in the pair, the platform must convert the result into your base currency using relevant exchange rates. This is why two traders using the same price move can still see different P/L amounts if their account base currencies differ.
Example checks you can do independently
You can verify the mechanics without predicting outcomes: (1) compare bid/ask quotes at the moment you enter; (2) track the exact entry and exit prices used in your order history; (3) check how the platform converts the pair’s valuation into your account base currency on your statement; and (4) confirm how the platform reports costs such as spread and any fees.
Limitations and risks
Forex trading involves uncertainty because exchange rates change for many reasons. Leverage or margin (where used) can amplify both gains and losses and can create obligations if equity falls below requirements. Also, execution is not guaranteed at a chosen price for certain order types, especially during fast price changes. Finally, measuring outcomes in your account base currency can add conversion effects that are independent of the pair’s raw price move.