Notarization is literally a legal way of certifying document copies. The notarized copy must contain a statement of notarization indicating that the copy corresponds to the original document, with the signature of the notary and official stamp with an emblem. There should be an official seal usually round and contain an emblem. Notarization can be done by lawyers, at high court or much better at the German Embassy in your home country.
Please find detailed information about notarization on tum.de.
Please find detailed information about notarization on tum.de.