Currency Pair is a traditional way to express the relative value of a currency one country unit against a unit of another currency in foreign exchange markets. A conventional way to express currency exchange rates is to express conversion rates in units of the second currency (called Quote currency or Counter currency) for 1 unit of Base currency. For instance, a quote of GBPUSD = 1.0500 means that one Pound Sterling (GBP) is worth 1.05 US Dollars.
Currency pairs are generally written by concatenating the ISO currency codes (ISO 4217) of the base currency and the counter currency, and then separating the two codes with a slash. Alternatively, the slash may be omitted, or replaced by either a dot or a dash.