This has been described in Ukrainian media as an investigative step which documents allegations against an individual or individuals, similar to a criminal referral. While Donibsky says during the press conference that "Zlochevsky was charged," we have updated our headline and report accordingly.
A transcription of key portions of the press conference can found here, via Tanya Tay Posobiec.
Update: Reuters sheds additional light on the press conference, noting that the document from the Prosecutor General's office was leaked and not officially released.
A Ukrainian MP says a document leaked from the Ukraine's Office of the Prosecutor General contains claims against Burisma owner Nikolai Zlochevsky, as well as Hunter Biden and his partners - who allegedly received $16.5 million for their 'services' - according to Alexander Dubinsky of the ruling Servant of the People Party.