What’s an editor?
Editors are an interface between the text and its intended readership.
They scrutinize the text to ensure it is as good as it can be, while keeping it as faithful to the original as possible.
The process usually goes something like this. Once you’ve engaged an editor, and given them your manuscript, they will look at its structure, syntax, grammar, spelling, consistency, accuracy, tone, pace, readability and credibility, among other characteristics. They will edit it accordingly; they may move material, or cut it, or ask you to make additions, among other things. They’ll then hand the file back to you to review the edit. You don’t have to accept all their changes, and you have every right to ask them for explanations. (The editing process should seem more like a conversation than a one-way critique.) Sometimes the text passes back and forth a couple more times for fine-tuning. Once you’ve agreed the edit with them, the text should be ready to go into layout.