In Germany a certified translation can only be issued by translators who have taken a certain examination and have been sworn-in and publicly appointed by an official authority. Translators and interpreters have to swear an oath that they will faithfully and conscientiously carry out their profession, and that they will explicitly indicate when they are not sure about the correctness of the translation.
Translators are also required to indicate any discrepancies in the document (words that have been crossed out, handwritten notes etc.)
The translation thus becomes a certification, which can be given further legality if it is legalised. The translator includes a certification note and an official stamp to confirm that the translation is correct.
A certified translation by a translator does not confirm the authenticity of the original document. Depending on the intended use and origin of the document, this has to be done by a notary or the responsible authority.