Forex Currencies are traded in pairs. Each currency is represented with a three letter abbreviation and is usually separated from the currency it is paired with a space, a point, or a slash. For instance, EUR/USD refers to the Euro US Dollar currency pair. 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 value of the pair is defined by how much of the quote currency is required to purchase a single unit of the base currency. So if EUR/USD is currently trading at 1.31 then this means that $1.31 is required to purchase €1.