The primary purpose of the CE marking (CE mark) is to simplify the free trade of products within the EU. The CE label proves that the product meets the minimum product safety requirements in the directive(s). Most products need to be CE marked if they're sold within the EU.
If a product comes under the scope of a directive requiring CE marking, the manufacturer must ensure it complies with the applicable requirements. Afterwards, the manufacturer has to affix the CE mark to the product, before introducing it to the EEA market.