In a publishing house, after the content editor, in consultation with the author, finalizes the manuscript and considers it solid at the big-picture level, the manuscript will move on to a copyeditor.
The copyeditor reads at a more micro level. The macro work has been completed, so the copyeditor focuses on every paragraph, every sentence, every word, every bit of punctuation. She reads closely for sentence construction—looking for dangling or misplaced modifiers, run-ons, lack of parallelism, correct subject and verb forms. He fact checks and queries if something doesn’t make sense. She marks if a transition is needed. He checks spelling, grammar, and punctuation and works to be correct without changing the author’s voice or stylistic choices. (Yes, sentence fragments are often just fine.)
PWR Blog 