Initially, I also am not clear about it. But when I compare documents as original, certified true copy and authenticated, makita ko ang pagkakaiba.
Original is initial set of prints with original signatures. There can be several original copies.
Certified True Copy is a photocopy of the original but certified by a 3rd party that indeed the copy is the same as the original. The stamps, signatures and certification are in original form on the photocopy. This is the copy you get when you request for a legal document from the archives of the Hall of Justice or Transfer Certificate of Title you are issued at Register of Deeds printed in paper. Certification merely states that the document is the same as the original. It may in substance be faulty or not.
Authenticated is an original or a photocopy further attested to its genuineness by a respected, recognized issuing control party. This can be NSO through its security paper, or the DFA through its red ribbon. Artworks are authenticated by a body.
The difference among the three is their degree of integrity. Authenticated has the highest level of integrity, followed by original and then the Certified True Copy.
Pag parehong dokumento ang pinaguusapan at submission sa isang government agency, parang walang pagkakaiba.
Pero sa pagkabigat ng ebidensya, doon mo mapapahalagahan ang pagkakaiba.