What is the difference between the CE mark and others like IMQ and VDE?

The CE mark is an EU requirement and it means that the products comply with the relative norms and regulations, and may circulate freely in member countries. It is the responsibility of the manufacturer or importer to ensure this mark is applied to products that meet the requirements. The IMQ, VDE, etc., marks are voluntary marks awarded by accredited third party institutions who certify that the product complies with technical standards, such as CEI, VDE etc.