EUR is the three-letter code used to abbreviate the euro, which is the currency of the Eurozone. Of the 28 member states of the European Union, 19 use the euro as their official currency.
Prior to having a physical single currency, the European Union used the ECU (European Currency Unit) as a unit of account between member states.
It was replaced on January 1st, 1999 with the introduction of the euro into the financial markets and was followed on January 1st, 2002 by the circulation of physical notes and coins. In all currency pairs that feature the euro, it has the privilege of being the first, or base currency in the pair.