At some point during your writing process, you might start looking for an editor to help you out. But suddenly you see lots of different editing roles out there. What do they all do? Do you need to hire them all? Here’s a quick primer on the most common types of editing for your various stages of writing.

Developmental editing
Where you are in your writing phase: You’ve finished a rough draft and need big picture help. This could include content gaps, organization, structure, narrative, or dialogue. This phase should be done at least once (multiple times for novel-length items) before heading on to line or copyediting.
Line editing
Where you are in your writing phase: You have the ideas down but need help making your writing more engaging. You’ve already worked with someone else on the big picture, and now you need to focus on the lines. Also called substantive editing, this is where we focus on the craft of writing. Often this is synonymous with a heavy copyedit, where an editor will look for run-on sentences, repeated word usage, passages that can be tightened or spruced up, and other midlevel issues.
Copyediting
Where you are in your writing phase: You have worked with someone on big picture issues and perhaps line-level ones, and you now need to clean up the piece. Amy Einsohn offers the four Cs of copyediting: consistency, clarity, cohesion, and correctness, all in the name of communication. Copyeditors aren’t necessarily rewriting whole sentences (though they’ll certainly help you limit the use of weak sentence structures, like starting sentences with “there are” and “it is”); they focus on making everything consistent and coherent, which usually means using a specific style guide (such as CMS, APA, MLA, or AP) and dictionary as a reference.
Proofreading
Where you are in your writing phase: You’ve been edited in various levels and are itching to publish, but you need to get another pair of eyes on your work to look for typos and formatting issues. Very few changes should be happening at this point. Proofreaders look for typos, small things that need correcting (missing commas, switching a comma to an em dash, etc.), and formatting issues (missing hanging indents, consistent image placement, italics for terms, etc.).
If you can’t tell, a good piece of writing is shaped by a lot of different roles. And there’s an order to editors helping you with your piece—you don’t bother with a copyeditor while you’re still in the developmental phase. By knowing which stage of writing you are in, you can hire the right type of editor and not waste your time or money (or theirs).