Schengen Area: All four European Free Trade Association (EFTA) member states – Iceland, Liechtenstein, Norway, and Switzerland – have signed the Schengen Agreement, even though they are outside the EU. In addition, three European microstates – Monaco, San Marino, and the Vatican City – can be considered as de facto within the Schengen Area (labels are shown on wiki)
Schengen Area: The Schengen Area is the area comprising 26 European countries that have abolished passport and any other type of border control at their common borders, also referred to as internal borders. It mostly functions as a single country for international travel purposes, with a common visa policy. The Area is named after the Schengen Agreement.