Copy Editing

What is Copy Editing (CE)?
Commonly referred to as a CE, copy editing deals with grammar and style.
Grammar and style reviews address typical grammatical errors as well as setting styles that address types of writing -- usually this is driven by Chicago Manual of Style (CMOS), and converts raw text to publishing expectations.
Grammatical Errors
Grammatical errors include, but are not limited to: spelling, punctuation, sentence construction errors like dangling modifiers, capitalization errors, and so forth. The things your English teacher harped on.
Using Track Changes, so that you're aware of any corrections, I review and correct these issues. I will perform minor suggestions if there are clunky sentences, and if I feel that the correction needs explanation, I'll comment on why I made the change.
Style & Consistency
Style addresses things such as: How are internal thoughts set in typography? Are we following British or American English? How does CMOS set a.m. and p.m.
Consistency addresses things like: random character eye color changes, description of items/areas/setting, the spelling of the super-nifty magical item; author-established or real world-established facts. It also addresses things like "When this line is remembered, is it remembered the same way it was initially presented."
When and What?
When --
A copy edit should only be performed once all story edits are completed. Changes in story after a CE would demand that new text, modified text, sections that have had text deleted need to be re-copy edited.
What --
You receive three documents when the CE is completed: the edited manuscript, a proper names document, and a style guide that logs the established styles.