A currency pair is the measure of the value of one currency against another. Currencies are listed in pairs such as EUR/USD or USD/JPY. The first listed currency of a pair is known as the base currency and the second is the quote currency.
A widely traded currency pair is the euro
against the U.S. dollar shown as EUR/USD. It is actually the most liquid currency pair in the world because it is the most heavily traded.
All currency pairs have a bid and ask price. The bid price is the maximum price a buyer is willing to pay for a currency pair, and the ask price is the minimum price a seller is willing to accept. The difference between the two prices is known as the spread.