Bid-Ask Spread
The difference between the highest price a buyer will pay and the lowest price a seller will accept for a currency.
Full Explanation
In currency trading, the bid price is what buyers will pay for a currency, and the ask price is what sellers want. The spread is the difference between these two prices. This spread is how market makers and payment providers make profit. A tighter spread (smaller difference) is better for you. For example, if USD/EUR bid is 0.85 and ask is 0.86, the spread is 0.01 (1 cent).