Thanks to the entry into force of the Schengen Agreement in 1985, it is possible to move freely between the States that make up the Schengen area, since it is a free movement zone in which there are no border controls. You have all the information in: «The Schengen area and the Member States of the European Union«.
You have all the information in: "The Schengen area and the Member States of the European Union".