Currencies are quoted in pairs, each being represented by a three-letter code separated by a forward slash, point or space. The first currency in the pair is known as the base currency, the second currency in the pair is known as the quote currency. The figure provided in an exchange rate refers to how much of the quote currency is required to purchase a unit of the base currency. So if GBP/USD is currently trading at 1.54785, this means that it costs $1.54 to purchase £1.