With the EU declaration of conformity, the "responsible manufacturer" or his authorised representative (based in the EU) confirms under his sole responsibility and in a legally binding manner that a product he has placed on the market complies with the essential health and safety requirements of all relevant European directives, i.e. that it conforms to them.

The EU declaration of conformity is a mandatory requirement for CE marking and placing the corresponding product on the market in the European Economic Area.

[Wikipedia / Further explanation (not available in English): de.wikipedia.org/wiki/EU-Konformit%C3%A4tserkl%C3%A4rung]