This is the price of one currency expressed in terms of the price other. In fact, this quote (see), ie the price of the currency pair, is recorded at the end of the trading day (session - see). For example, the trading session the pair EUR / USD (euro / dollar) was completed at around 1,238. This means that the Central banks announce that the euro is 1,238 dollars. This rate will last for the entire day, until the end of the next trading day.