It's one of the most asked questions. What actually is the difference? There are many stages when it comes to publishing, and in this post I'll break them down to make them a bit easier to understand.
The first and most important part – the writing! There needs to actually be something to edit; so obviously the first part in the publishing process is getting the words down onto paper (or a computer, we're in the 21st century after all).
After you've jotted, scribbled, typed manically and your fingers are aching, you get to sit back and have a breather. But, once you've recovered and drank numerous cups of coffee (or gin?) you need to edit the piece yourself. Have a look at my post about tips & tricks for proofreading your own work if you struggle with this part.
Ok, so you've read and re-read it hundreds of times. Those tiny little errors still sneak through, because your brain skips over them. It's completely normal. The next step though (if we're talking about a novel) is to seek a developmental editor. They will check the overall structure of the manuscript; making sure it actually makes sense. They make sure that the characters are engaging and that the story flows well.
The next person in the editing process is the copyeditor/line editor. The best way to describe the copyeditor/line editor is that they look at the copy on a line by line/word by word basis. They check for any obvious errors that you've missed, as well as making suggestions for small amendments to improve the text. This process can take time – the document could go back and forth between the copyeditor and the author numerous times in fact!
Now we get to the proofreader. The proofreader takes it one step further than the copyeditor, and reads the text letter by letter! Making sure there is nothing that has slipped through the cracks. The proofreader is the absolute final stop check before you get your printed copy. Nobody else checks the document again after the proofreader, meaning their work is very important.
So basically, what's the difference between a proofreader and a copyeditor?
A copyeditor checks the writing on a line by line/word by word basis, whereas a proofreader checks the writing letter by letter.
That's the most simple way of explaining the difference.