I believe an editor's job is to preserve and enhance the author's voice while ensuring excellence of story, style, and wording.
Depending on which service you choose, I guarantee between two and four rounds of work on your manuscript, which means you can concentrate your energy on all the other aspects of publishing you have to take care of—without worrying about the technicalities of language, grammar, and punctuation.
While editing, I try always to explain the reasons behind the less obvious of my suggestions. This means you can follow my way of thinking and make informed choices about whether to accept, reject, or adapt the suggestions. It will also help you when you self-edit your next book. At all times, we'll stay in touch with each other, and between rounds, I'll address any comments or queries you've left in the manuscript. My editing includes informal sensitivity reading, so if it cropped up, I would also highlight anything I feel might offend your defined audience and leave it in your capable hands to make the final decision.
Proofreading is a lot simpler, but I believe communication is key here, as well.
Finally, I thoroughly enjoy my job, and my hope is that you'll enjoy it too. I promise always to be honest, constructive, and kind!