As of August 2018, below is a current list of the 26 European Schengen Nations. They allow registrants to visit:
Austria
Belgium
Czech republic
Denmark
Estonia
Finland
France
Germany
Greece
Hungary
Iceland
Italy
Latvia
Liechtenstein
Lithuania
Luxembourg
Malta
Netherlands
Norway
Poland
Portugal
Slovakia
Slovenia
Spain
Sweden
Switzerland
As an agreement, Schengen was signed among the five out of ten countries of the European Union members back then, on the 14th June 1985. Under the Schengen agreement, travelling from one Schengen country to another is done without any passport and immigration controls or any other formalities previously required.