The Schengen Area is a border-free travel zone of 29 European countries that have abolished routine checks at their shared internal borders, so people can usually move between member states without passport controls. It includes 25 EU member states plus Iceland, Norway, Switzerland, and Liechtenstein; Ireland remains outside under an opt-out, and Cyprus is still completing full integration.
External borders stay controlled under common rules. Many short-stay visitors use a Schengen visa that allows free movement within the area for up to 90 days in any 180-day period. Source: European Commission – Schengen area.