For an editing project, a second translator checks the completed translation for accuracy, tone, grammar, punctuation, and noting any translation errors in the Editor Report before a revised file is send to the client. They're called as PostTranslationProofreadingProject projects in your Open projects page:

You'll see the project brief (notes), original source, and translated target files. The editor checks the translation against the source and corrects all mistakes, considering the instructions in the Project Brief.

Copy/paste any lines of text containing an error into the Editor Report on the project page. This step is required and helps BLEND determine the quality of the initial translation.
Once all errors are fixed and the Editor Report finish, upload the final, revised target file to the project page and sign the project.

As an editor, you are responsible for providing the final translation to the client.