This is is how much a national currency of one country is willing to pay for currency of another country at the moment. When people talk about the exchange rate, always have in mind some currency pair. An illustrative example is a daily statement of the Central Bank of Russia saying: "the official dollar exchange rate is 36 rubles 80 kopecks." It means that for one dollar today, they will give 36.80 rubles. For example, take the euro/dollar pair (EUR/USD). Assume that its quote (see) currently is 1,238. It means that now the market is willing to pay 1.238 dollars for one euro. After a few seconds for the euro is already 1,239, and five minutes later 1.237. It is exactly from the constant changes in the exchange rates that market traders earn.