The copyedit is for the author who is ready to look at sentence-level perfection. Ideally, you have done all your developmental editing before this phase. During the developmental editing process, things tend to move around or there are changes in point of view or tense, and there can be pieces of the old version left behind. Copyediting looks for those, but it also seeks to tighten up sentences. With a copyedit, if you choose, you can receive a style sheet with the copyedited manuscript. This sheet is useful for proofreading and any potential series work. It is a tool to ensure consistency in areas such as spelling of names and punctuation styles. 

In addition to catching spelling and grammar errors, the copyedit focuses on:
-sentence structure
-word choice
-consistency in story, style, voice, and spelling
-author voice
​-eliminating repetition
-identifying and eliminating filler words ("just" and "well" are common ones)

Copyediting starts at $0.01/word. 

I make all changes using Word's Track Changes tool, and all suggestions are entered using the Comments tool. If you have never used these before, I can provide a document explaining them.