Both Schengen countries and EU countries are European countries. However, not all EU nations are part of the Schengen Zone.
The European Union (EU) is a unique economic and political union of 28 member states that have developed a single market and that are bound by mutual judicial and legislative institutions. EU policies aim to ensure the free movement of people, goods, services, and capital within the internal market, enact legislation in justice and home affairs, and maintain common policies. In 1999 a monetary union was established, and on 1 January 2002, physical euro coins and banknotes entered into circulation. Currently, 19 EU member states use the Euro (EUR – €) as their currency.
The Schengen Area is comprised of 26 European countries of which only 4 are not members of the EU. These four countries are Iceland, Norway, Switzerland, and Liechtenstein. Schengen area countries have abolished passports, and any other type of border control at their shared borders also referred to as internal borders. The border-free Schengen Area guarantees free movement of goods and more than 400 million EU citizens, as well as many non-EU nationals.