'Euro' is explained in detail and with examples in the Economics edition of the Herold Financial Dictionary, which you can get from Amazon in Ebook or Paperback edition.
The Euro proves to be the one currency that fully 19 of the member countries of the European Union share. These nations are said to belong to the Euro area, or Euro zone. This currency became introduced in 1999 and marked a major milestone in the attempted integration of the member countries in the European continent. The currency today remains among its greatest of successes, though it has suffered from problems in the European Sovereign Debt Crisis.
Over 337.5 million citizens of the European Union use this shared currency in 19 nations. Though most of the EU countries enjoy the benefits a single currency conveys, not all have chosen to use it. Several of the member nations in the Euro zone have not met the necessary criteria to switch currencies, such as with Hungary, Romania, and Bulgaria. Sweden has not yet voluntarily moved to adopt the currency. Two other nations have opt-out exemption rights from the currency in their individual treaties. These are the United Kingdom (which is in the process of leaving the European Union after its pro Brexit referendum vote) and Denmark.
The actual introduction of the world’s second reserve currency began in 1999 when the initial Euro zone nations rolled it out as accounting entries, or “book money.” Physical coins and notes appeared in 2002. Proponents of the European Union project call it among their greatest of accomplishments. These notes and coins are an everyday commercial presence in the lives of the various different peoples that make up these 19 individual countries.
It required a number of years of preparation and planning to come up with the final design of the Euros themselves. The monetary authorities wanted to strike the right balance of security features, appearance, and practical aspects when they created them. In January of 2002, the European Central Bank and various national central banks had eight coins and seven bank notes created for the official launch. The notes carry the identical designs for all nations in the Euro zone. The coins are unique to each country.
One side of the coins features a common design. The other side is specific to each individual nation. Every country designed its own national side. Common sides include one of three varying maps of the continent of Europe and have a background that features the 12 stars representing the European Union. In 2007, the mints modified common side designs so that they showed the 2004 enlargement of the European Union. This affected all coins including the 1 and 2 Euros coins and the 50, 20, and 10 cent pieces. The design became mandatory in future coin production beginning in 2008.
Though each nation has its own central bank, it is the ECB European Central Bank that reserves the exclusive privilege of authorizing creation of additional Euro banknotes via the different national central banks. Production and circulation of these notes is a shared responsibility of all of the countries’ central banks. National mints produce the coins according to volumes that the ECB approves every year.
In 2013, the central banks began introducing their new and improved Europa series of bank notes. This began with the new five Euros bill introduced on May 2, 2013. Improved technology allowed for better security features to fight against the increasingly common practice of counterfeiting these notes. As part of the revision, the bank notes were modified so that they had an updated appearance.