Certification
Certification generally means vouching that a product complies with a certain requirement, such as a government standard.
The term "certificate of conformity" means a written guarantee that a particular product meets the requirements applied to it. In order to issue such a written guarantee, i.e. the certificate of conformity, one shall have a basis or assurance for that.
The certification body acquires this assurance by an examination of characteristics and production procedures of the product to be certified (technical characteristics) whether they really meet the requirements set, which are usually specified in the technical specification (standard) for the product.
Conformity Assessment
At its simplest, "conformity assessment" means checking that products, materials, services, systems or people measure up to the specifications of a relevant standard. For example, a customer may want to check that the product he or she ordered from a supplier meets the purpose for which it is required. One of the most efficient ways to do this is when the specifications of the product have been defined in an International Standard. That way, both supplier and customer are on the same wavelength, even if they are based in different countries, because they are both using the same references.