This is a declaration by the manufacturer or by an importer located within the European Economic Area that the product complies with the essential health and safety requirements of the relevant EU directives.
Products being sold in or, respectively, imported into the European Union have to comply with this EU-directive and, for confirmation, have to carry a visible CE-marking. This applies to more than 80% of all industrial and consumer products. Sale without a CE-marking within the EU is not permitted.