The euro area is a monetary union. In order to have a monetary union, there must be a situation in which at least two countries share the same official currency. In the euro area, this requirement is met. In other words, more than two countries have the euro as their official currency. Specifically, there are 19 states.
Created in 1834, Zollverein was an economic organization by German termed as a customs union under Prussian leadership. Numerous German states joined forces to create a free trade zone and establish customs tariffs against third countries.
The Single Euro Payments Area (SEPA) is a collective association created in Europe that allows companies, individuals and public bodies to make payments in euros without using cash. These payments can be made using a single bank account for payment transactions in different part of Europe within the SEPA zone.